Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.24% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-35188High confidence
Double-free When Checking OCSP Stapled Response
OpenSSL · OpenSSL
5.0MediumCVSS 3.1
Scheduled
Patch availableMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs OpenSSL OpenSSL and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Distribution package intelligence
4 package statesRelease-specific package status
Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | openssl | Not affectedDebian marks this release not affected (fixed-version marker 0). | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian bookwormbookworm · source | openssl | Not affectedDebian marks this release not affected (fixed-version marker 0). | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian forkyforky · source | openssl | Vendor fix publishedDebian records a fixed source-package version for this release. | 3.6.3-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian sidsid · source | openssl | Vendor fix publishedDebian records a fixed source-package version for this release. | 3.6.3-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2026-35188 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityopenssl: Double-free When Checking OCSP Stapled Response
The vendor explicitly identifies these products or versions as containing the fix.
- bootupd-0:0.3.2-1.hum1@aarch64 as a component of Red Hat Hardened Images
- bootupd-0:0.3.2-1.hum1@x86_64 as a component of Red Hat Hardened Images
- chunkah-0:0.6.0-3.hum1@aarch64 as a component of Red Hat Hardened Images
- chunkah-0:0.6.0-3.hum1@src as a component of Red Hat Hardened Images
- chunkah-0:0.6.0-3.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-0:3.5.8-0.1.hum1@src as a component of Red Hat Hardened Images
- openssl-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-config-fips-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-config-fips-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-devel-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-devel-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- Summary
- A flaw was found in OpenSSL. A malicious server can exploit the TLS Online Certificate Status Protocol (OCSP) stapling feature by sending a specially crafted response. This can trigger a double-free vulnerability in the client's certificate verification process, potentially leading to a Denial of Service (DoS) or, with greater technical complexity, arbitrary code execution. This issue occurs when OCSP stapling is enabled, which is not the default configuration.
- Remediation
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available01
What, why and how
Issue summary: A malicious server can exploit TLS OCSP stapling by delivering a crafted response through the status_request extension, triggering a double-free in the client's certificate verification path. Impact summary: Successful exploitation allows an attacker to corrupt heap memory via a double-free, potentially leading to a Denial of Service or possibly an attacker controlled code execution or other undefined behavior. If OCSP stapling is enabled and the TLS client connects to a malicious server, a crafted OCSP stapled response can trigger a double free in the TLS client when the stapled response is checked. The OCSP stapling is not enabled by default. Reliable code execution through a double-free is technically complex and highly environment-dependent but the Denial of Service impact is straightforward to achieve, warranting Moderate severity. No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.
What
Issue summary: A malicious server can exploit TLS OCSP stapling by delivering a crafted response through the status_request extension, triggering a double-free in the client's certificate verification path. Impact summary: Successful exploitation allows an attacker to corrupt heap memory via a double-free, potentially leading to a Denial of Service or possibly an attacker controlled code execution or other undefined behavior. If OCSP stapling is enabled and the TLS client connects to a malicious server, a crafted OCSP stapled response can trigger a double free in the TLS client when the stapled response is checked. The OCSP stapling is not enabled by default. Reliable code execution through a double-free is technically complex and highly environment-dependent but the Denial of Service impact is straightforward to achieve, warranting Moderate severity. No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.
Why
The product calls free() twice on the same memory address.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.
What
Issue summary: A malicious server can exploit TLS OCSP stapling by delivering a crafted response through the status_request extension, triggering a double-free in the client's certificate verification path. Impact summary: Successful exploitation allows an attacker to corrupt heap memory via a double-free, potentially leading to a Denial of Service or possibly an attacker controlled code execution or other undefined behavior. If OCSP stapling is enabled and the TLS client connects to a malicious server, a crafted OCSP stapled response can trigger a double free in the TLS client when the stapled response is checked. The OCSP stapling is not enabled by default. Reliable code execution through a double-free is technically complex and highly environment-dependent but the Denial of Service impact is straightforward to achieve, warranting Moderate severity. No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.
Why
The product calls free() twice on the same memory address.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Double Free → disrupt the affected service
- Attack surface
- Network
- Privileges required
- Low: a basic authenticated account is required
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-415 ↗
CWE-415: Double Free. The product calls free() twice on the same memory address.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:LCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.ILowIntegrity impact: A successful attack can cause a limited loss.ALowAvailability impact: A successful attack can cause a limited loss.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Patch available
- Fixed
- bootupd-0:0.3.2-1.hum1@aarch64 as a component of Red Hat Hardened Images
- bootupd-0:0.3.2-1.hum1@x86_64 as a component of Red Hat Hardened Images
- chunkah-0:0.6.0-3.hum1@aarch64 as a component of Red Hat Hardened Images
- chunkah-0:0.6.0-3.hum1@src as a component of Red Hat Hardened Images
- chunkah-0:0.6.0-3.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-0:3.5.8-0.1.hum1@src as a component of Red Hat Hardened Images
- openssl-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-config-fips-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-config-fips-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-devel-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-devel-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-devel-engine-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-devel-engine-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-fips-provider-upstream-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-fips-provider-upstream-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-libs-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-libs-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl-perl-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl-perl-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl3-0:3.5.8-0.1.hum1@src as a component of Red Hat Hardened Images
- openssl3-devel-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl3-devel-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl3-devel-engine-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl3-devel-engine-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- openssl3-libs-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images
- openssl3-libs-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images
- python-cryptography-0:50.0.0-1.hum1@src as a component of Red Hat Hardened Images
- python3-cryptography-0:50.0.0-1.hum1@aarch64 as a component of Red Hat Hardened Images
- python3-cryptography-0:50.0.0-1.hum1@x86_64 as a component of Red Hat Hardened Images
- and 40 more
- Action
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 9 Jun 2026 · Last source change 10 Jun 2026, 20:02 UTC · CWE-415 · Double Free
CVE recordCVE.org · 5.2
CVSS sourceCISA ADP
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-35480
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- 4.0.0 < 4.0.1; 3.6.0 < 3.6.3 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
- After
- 4.0.0 < 4.0.1; 3.6.0 < 3.6.3 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-35188 to remediation: access.redhat.com/CVE-2026-35188.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-35188
- After
- remediation: access.redhat.com/CVE-2026-35188
- Remediation statusRemediation status changed from Mitigation available to Patch available.Red Hat Product Security ↗
- Before
- Mitigation available
- After
- Patch available
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- chunkah.src as a component of Red Hat Hardened Images; openssl.src as a component of Red Hat Hardened Images; openssl3.src as a component of Red Hat Hardened Images; python-cryptography.src as a component of Red Hat Hardened Images; ruby3.3.src as a component of Red Hat Hardened Images; ruby3.4.src as a component of Red Hat Hardened Images; ruby4.0.src as a component of Red Hat Hardened Images; rust-bootupd.src as a component of Red Hat Hardened Images
- After
- Fixed: bootupd-0:0.3.2-1.hum1@aarch64 as a component of Red Hat Hardened Images; bootupd-0:0.3.2-1.hum1@x86_64 as a component of Red Hat Hardened Images; chunkah-0:0.6.0-3.hum1@aarch64 as a component of Red Hat Hardened Images; chunkah-0:0.6.0-3.hum1@src as a component of Red Hat Hardened Images; chunkah-0:0.6.0-3.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-0:3.5.8-0.1.hum1@src as a component of Red Hat Hardened Images; openssl-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-config-fips-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-config-fips-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-devel-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-devel-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-devel-engine-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-devel-engine-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-fips-provider-upstream-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-fips-provider-upstream-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-libs-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-libs-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl-perl-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl-perl-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl3-0:3.5.8-0.1.hum1@src as a component of Red Hat Hardened Images; openssl3-devel-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl3-devel-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl3-devel-engine-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl3-devel-engine-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; openssl3-libs-0:3.5.8-0.1.hum1@aarch64 as a component of Red Hat Hardened Images; openssl3-libs-0:3.5.8-0.1.hum1@x86_64 as a component of Red Hat Hardened Images; python-cryptography-0:50.0.0-1.hum1@src as a component of Red Hat Hardened Images; python3-cryptography-0:50.0.0-1.hum1@aarch64 as a component of Red Hat Hardened Images; python3-cryptography-0:50.0.0-1.hum1@x86_64 as a component of Red Hat Hardened Images; and 40 more
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- chunkah.src as a component of Red Hat Hardened Images; openssl.src as a component of Red Hat Hardened Images; openssl3.src as a component of Red Hat Hardened Images; python-cryptography.src as a component of Red Hat Hardened Images; ruby3.3.src as a component of Red Hat Hardened Images; ruby3.4.src as a component of Red Hat Hardened Images; ruby4.0.src as a component of Red Hat Hardened Images; rust-bootupd.src as a component of Red Hat Hardened Images; unbound.src as a component of Red Hat Hardened Images
- After
- chunkah.src as a component of Red Hat Hardened Images; openssl.src as a component of Red Hat Hardened Images; openssl3.src as a component of Red Hat Hardened Images; python-cryptography.src as a component of Red Hat Hardened Images; ruby3.3.src as a component of Red Hat Hardened Images; ruby3.4.src as a component of Red Hat Hardened Images; ruby4.0.src as a component of Red Hat Hardened Images; rust-bootupd.src as a component of Red Hat Hardened Images
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-35188 to remediation: access.redhat.com/CVE-2026-35188.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-35188
- After
- remediation: access.redhat.com/CVE-2026-35188
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Mitigation available
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- After
- chunkah.src as a component of Red Hat Hardened Images; openssl.src as a component of Red Hat Hardened Images; openssl3.src as a component of Red Hat Hardened Images; python-cryptography.src as a component of Red Hat Hardened Images; ruby3.3.src as a component of Red Hat Hardened Images; ruby3.4.src as a component of Red Hat Hardened Images; ruby4.0.src as a component of Red Hat Hardened Images; rust-bootupd.src as a component of Red Hat Hardened Images; unbound.src as a component of Red Hat Hardened Images
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-35188 to remediation: access.redhat.com/CVE-2026-35188.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-35188
- After
- remediation: access.redhat.com/CVE-2026-35188
- Remediation statusRemediation status changed from Mitigation available to Awaiting fix.Red Hat Product Security ↗
- Before
- Mitigation available
- After
- Awaiting fix
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- jbcs-httpd24-openssl as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-devel as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-libs as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-perl as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-static as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl.src as a component of Red Hat JBoss Core Services; jbcs-openssl-win6-x86_64.zip as a component of Red Hat JBoss Core Services
- After
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-35188 to remediation: access.redhat.com/CVE-2026-35188.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-35188
- After
- remediation: access.redhat.com/CVE-2026-35188
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Mitigation available
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- After
- jbcs-httpd24-openssl as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-devel as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-libs as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-perl as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl-static as a component of Red Hat JBoss Core Services; jbcs-httpd24-openssl.src as a component of Red Hat JBoss Core Services; jbcs-openssl-win6-x86_64.zip as a component of Red Hat JBoss Core Services
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.