Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 60.27% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2019-17567High confidence
mod_proxy_wstunnel tunneling of non Upgraded connections
Apache Software Foundation · Apache HTTP Server
5.3MediumCVSS 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:High, raised one band.upgradedsince 23 Oct 2026
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 Apache Software Foundation Apache HTTP Server 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 | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.48-2 | Debian Security Tracker ↗Source updated 23 Oct 2026 |
| Debian bookwormbookworm · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.48-2 | Debian Security Tracker ↗Source updated 23 Oct 2026 |
| Debian forkyforky · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.48-2 | Debian Security Tracker ↗Source updated 23 Oct 2026 |
| Debian sidsid · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.48-2 | Debian Security Tracker ↗Source updated 23 Oct 2026 |
Direct vendor intelligence
0 current · 1 archivedAuthoritative 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-2019-17567 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityhttpd: mod_proxy_wstunnel tunneling of non Upgraded connectionNo longer in the provider’s current catalogue
The vendor explicitly identifies these products as affected by this CVE.
- httpd as a component of Red Hat Enterprise Linux 7
- httpd-devel as a component of Red Hat Enterprise Linux 7
- httpd-manual as a component of Red Hat Enterprise Linux 7
- httpd-tools as a component of Red Hat Enterprise Linux 7
- httpd.src as a component of Red Hat Enterprise Linux 7
- mod_ldap as a component of Red Hat Enterprise Linux 7
- mod_proxy_html as a component of Red Hat Enterprise Linux 7
- mod_session as a component of Red Hat Enterprise Linux 7
- mod_ssl as a component of Red Hat Enterprise Linux 7
- httpd-devel (httpd:2.4) as a component of Red Hat Enterprise Linux 8
- httpd-filesystem (httpd:2.4) as a component of Red Hat Enterprise Linux 8
- httpd-manual (httpd:2.4) as a component of Red Hat Enterprise Linux 8
- Summary
- A flaw was found in Apache httpd. The mod_proxy_wstunnel module tunnels non-upgraded connections.
- Remediation
- Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
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
Apache HTTP Server versions 2.4.6 to 2.4.46 mod_proxy_wstunnel configured on an URL that is not necessarily Upgraded by the origin server was tunneling the whole connection regardless, thus allowing for subsequent requests on the same connection to pass through with no HTTP validation, authentication or authorization possibly configured.
What
Apache HTTP Server versions 2.4.6 to 2.4.46 mod_proxy_wstunnel configured on an URL that is not necessarily Upgraded by the origin server was tunneling the whole connection regardless, thus allowing for subsequent requests on the same connection to pass through with no HTTP validation, authentication or authorization possibly configured.
Why
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
Apache HTTP Server versions 2.4.6 to 2.4.46 mod_proxy_wstunnel configured on an URL that is not necessarily Upgraded by the origin server was tunneling the whole connection regardless, thus allowing for subsequent requests on the same connection to pass through with no HTTP validation, authentication or authorization possibly configured.
Why
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
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 → Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- 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-444 ↗
CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'). The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
- 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:L/PR:N/UI:N/S:U/C:N/I:L/A:NCommon 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.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.ILowIntegrity impact: A successful attack can cause a limited loss.ANoneAvailability impact: No direct loss is represented by this metric.- 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
- Action
- Apply the fixed release for the affected product branch as recorded by Red Hat Product Security. Validate the exact product and build in the linked advisory before deployment.
- Workaround
- A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04
Evidence and provenance
Published 10 Jun 2021 · Last source change 5 Aug 2024, 01:40 UTC · CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
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-2019-7905
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2019-17567 to advisory no longer present in the provider's current catalogue.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2019-17567
- After
- advisory no longer present in the provider's current catalogue
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- 2.4.46; 2.4.43; 2.4.41; 2.4.39; 2.4.38; 2.4.37; 2.4.35; 2.4.34 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- 2.4.46; 2.4.43; 2.4.41; 2.4.39; 2.4.38; 2.4.37; 2.4.35; 2.4.34 · Fixed: Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
- Remediation statusRemediation status changed from Mitigation available to Patch available.Red Hat Product Security ↗
- Before
- Mitigation available
- After
- Patch available
CVE published
Mitigation 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.