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Full vulnerability report · 2026
CVE-2026-28386High confidence

Out-of-bounds Read in AES-CFB-128 on X86-64 with AVX-512 Support

OpenSSL · OpenSSL

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

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 0.33% for the current model date.

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

  1. Confirm that the asset runs OpenSSL OpenSSL and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-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.

4 package states
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 releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourceopensslNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourceopensslNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourceopensslVendor fix publishedDebian records a fixed source-package version for this release.3.6.2-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourceopensslVendor fix publishedDebian records a fixed source-package version for this release.3.6.2-1Debian Security Tracker ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative 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.

1 current
CVE-2026-28386 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityopenssl: openssl: Denial of Service due to out-of-bounds read in AES-CFB128
35 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • edk2-aarch64 as a component of Red Hat Enterprise Linux 10
  • edk2-ovmf as a component of Red Hat Enterprise Linux 10
  • edk2-tools as a component of Red Hat Enterprise Linux 10
  • edk2-tools-doc as a component of Red Hat Enterprise Linux 10
  • edk2.src as a component of Red Hat Enterprise Linux 10
  • mokutil as a component of Red Hat Enterprise Linux 10
  • shim-aa64 as a component of Red Hat Enterprise Linux 10
  • shim-unsigned-aarch64.src as a component of Red Hat Enterprise Linux 10
  • shim-unsigned-x64.src as a component of Red Hat Enterprise Linux 10
  • shim-x64 as a component of Red Hat Enterprise Linux 10
  • AAVMF as a component of Red Hat Enterprise Linux 7
  • OVMF as a component of Red Hat Enterprise Linux 7
Summary
A flaw was found in openssl. Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support may experience a Denial of Service (DoS). This occurs when processing partial cipher blocks, specifically if the input buffer ends at a memory page boundary and the subsequent page is unmapped. This can lead to an out-of-bounds read of up to 15 bytes and a potential application crash.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-19958

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Issue summary: Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support can trigger an out-of-bounds read of up to 15 bytes when processing partial cipher blocks. Impact summary: This out-of-bounds read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not written to output. The vulnerable code path is only reached when processing partial blocks (when a previous call left an incomplete block and the current call provides fewer bytes than needed to complete it). Additionally, the input buffer must be positioned at a page boundary with the following page unmapped. CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or ChaCha20-Poly1305 instead. For these reasons the issue was assessed as Low severity according to our Security Policy. Only x86-64 systems with AVX-512 and VAES instruction support are affected. Other architectures and systems without VAES support use different code paths that are not affected. OpenSSL FIPS module in 3.6 version is affected by this issue.

What

Issue summary: Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support can trigger an out-of-bounds read of up to 15 bytes when processing partial cipher blocks. Impact summary: This out-of-bounds read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not written to output. The vulnerable code path is only reached when processing partial blocks (when a previous call left an incomplete block and the current call provides fewer bytes than needed to complete it). Additionally, the input buffer must be positioned at a page boundary with the following page unmapped. CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or ChaCha20-Poly1305 instead. For these reasons the issue was assessed as Low severity according to our Security Policy. Only x86-64 systems with AVX-512 and VAES instruction support are affected. Other architectures and systems without VAES support use different code paths that are not affected. OpenSSL FIPS module in 3.6 version is affected by this issue.

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

Issue summary: Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support can trigger an out-of-bounds read of up to 15 bytes when processing partial cipher blocks. Impact summary: This out-of-bounds read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not written to output. The vulnerable code path is only reached when processing partial blocks (when a previous call left an incomplete block and the current call provides fewer bytes than needed to complete it). Additionally, the input buffer must be positioned at a page boundary with the following page unmapped. CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or ChaCha20-Poly1305 instead. For these reasons the issue was assessed as Low severity according to our Security Policy. Only x86-64 systems with AVX-512 and VAES instruction support are affected. Other architectures and systems without VAES support use different code paths that are not affected. OpenSSL FIPS module in 3.6 version is affected by this issue.

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. 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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

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 → Out-of-bounds Read → disrupt the affected service
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-125 ↗

CWE-125: Out-of-bounds Read. The product reads data past the end, or before the beginning, of the intended buffer.

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:N/A:H

Common 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.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major 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.
NetworkUnauthenticatedDenial of serviceCWE-125
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-0995OpenSSL: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in OpenSSL ausnutzen, um einen Denial of Service Angriff durchzuführen, vertrauliche Informationen offenzulegen oder andere, nicht näher spezifizierte Angriffe durchzuführen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0796Multiples vulnérabilités dans Tenable Identity Exposure

ord?id=CVE-2026-21714 Référence CVE CVE-2026-21715 https://www.cve.org/CVERecord?id=CVE-2026-21715 Référence CVE CVE-2026-21716 https://www.cve.org/CVERecord?id=CVE-2026-21716 Référence CVE CVE-2026-21717 https://www.cve.org/CVERecord?id=CVE-2026-21717 Référence CVE CVE-2026-22795 https://www.cve.org/CVERecord?id=CVE-2026-22795 Référence CVE CVE-2026-22796 https://www.cve.org/CVERecord?id=CVE-2026-22796 Référence CVE CVE-2026-26130 https://www.cve.org/CVERecord?id=CVE-2026-26130 Référence CVE CVE-2026-26171 https://www.cve.org/CVERecord?id=CVE-2026-26171 Référence CVE CVE-2026-2673 https://www.cve.org/CVERecord?id=CVE-2026-2673 Référence CVE CVE-2026-28386 https://www.cve.org/CVERecord?id=CVE-2026-28386 Référence CVE CVE-2026-28387 https://www.cve.org/CVERecord?id=CVE-2026-28387 Référence CVE CVE-2026-28388 https://www.cve.org/CVERecord?id=CVE-2026-28388 Référence CVE CVE-2026-28389 https://www.cve.org/CVERecord?id=CVE-2026-28389 Référence CVE CVE-2026-28390 https://www.cve.org/CVERecord?id=CVE-2026-28390 Référence CVE CVE-2026-31789 https://www.cve.org/CVERecord?id=CVE-2026-31789 Référence CVE CVE-2026-31790 https://www.cve.org/CVERecord?id=CVE-2026-31790 Référence CVE CVE-2026-32167 https://www.cve.org/CVERecord?id=CVE-2026-32167 Référence CVE CVE-2026-32175 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0403Multiples vulnérabilités dans OpenSSL

De multiples vulnérabilités ont été découvertes dans OpenSSL. Elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance, un déni de service à distance et une atteinte à la confidentialité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-010838OpenSSLにおける複数の脆弱性（OpenSSL Security Advisory [7th April 2026]）

OpenSSL Projectから OpenSSL Security Advisory [7th April 2026] が公開されました。 深刻度 - 中（Severity: Moderate） RSA KEM RSASVEカプセル化における不適切なエラー処理（CWE-754、CVE-2026-31790） RSA_public_encrypt()において、RSA暗号化が失敗した際の戻り値判定が不適切なため、失敗していても成功として扱ってしまい、結果として出力バッファが未初期化のまま送信される可能性がある 深刻度 - 低（Severity：Low） AES-CFB-128処理時の境界外読み取り（CWE-125、CVE-2026-28386） AVX-512およびVAESをサポートするシステム上でAES-CFB128による暗号化または復号を行う場合、暗号ブロックを処理する際に最大15バイトの境界外読み取りが発生する DANEクライアントコードにおける解放済みメモリ使用（use-after-free）（CWE-416、CVE-2026-28387） DANE検証処理において、TLSAレコードの組み合わせにより解放済みメモリ使用（use-after-free）または二重解放（double free）が発生する Delta CRL処理時のNULLポインタ参照（CWE-476、CVE-2026-28388） Delta CRL Indicator拡張を含むDelta CRLを処理する際に、必須項目であるCRL Number拡張が欠落していると、NULLポインタ参照が発生する KeyAgreeRecipientInfo処理時のNULLポインタ参照（CWE-476、CVE-2026-28389） CMS EnvelopedDataメッセージを処理する際、KeyAgreeRecipientInfoの処理過程でKeyEncryptionAlgorithmIdentifierのフィールドが欠落しているとNULLポインタ参照が発生する CMS KeyTransportRecipientInfo処理時のNULLポインタ参照（CWE-476、CVE-2026-28390） CMS EnvelopedDataメッセージを処理する際、KeyTransportRecipientInfo処理過程でSourceFuncアルゴリズムのパラメータが欠落しているとNULLポインタ参照が発生する 16進数変換時におけるヒープベースのバッファオーバーフロー（CWE-787、CVE-2026-31789） 極端に大きなOCTET STRINGを16進文字列に変換する際、32bit環境においてヒープベースのバッファオーバーフローが発生する

Official advisory ↗
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
Affected
Fixed
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 7 Apr 2026 · Last source change 10 Apr 2026, 20:16 UTC · CWE-125 · Out-of-bounds Read

CVE recordCVE.org · 5.2
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-19958
Product sourceVendor CSAF · Red Hat Product Security
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

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    3.6.0 < 3.6.2 · 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
    3.6.0 < 3.6.2 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
    Red Hat Product Security ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    edk2-aarch64 as a component of Red Hat Enterprise Linux 10; edk2-ovmf as a component of Red Hat Enterprise Linux 10; edk2-tools as a component of Red Hat Enterprise Linux 10; edk2-tools-doc as a component of Red Hat Enterprise Linux 10; edk2.src as a component of Red Hat Enterprise Linux 10; mokutil as a component of Red Hat Enterprise Linux 10; shim-aa64 as a component of Red Hat Enterprise Linux 10; shim-unsigned-aarch64.src as a component of Red Hat Enterprise Linux 10; shim-unsigned-x64.src as a component of Red Hat Enterprise Linux 10; shim-x64 as a component of Red Hat Enterprise Linux 10; AAVMF as a component of Red Hat Enterprise Linux 7; OVMF as a component of Red Hat Enterprise Linux 7; ovmf.src as a component of Red Hat Enterprise Linux 7; edk2-aarch64 as a component of Red Hat Enterprise Linux 8; edk2-ovmf as a component of Red Hat Enterprise Linux 8; edk2.src as a component of Red Hat Enterprise Linux 8; shim-aa64 as a component of Red Hat Enterprise Linux 8; shim-ia32 as a component of Red Hat Enterprise Linux 8; shim-unsigned-x64 as a component of Red Hat Enterprise Linux 8; shim-unsigned-x64.src as a component of Red Hat Enterprise Linux 8; shim-x64 as a component of Red Hat Enterprise Linux 8; shim.src as a component of Red Hat Enterprise Linux 8; edk2-aarch64 as a component of Red Hat Enterprise Linux 9; edk2-ovmf as a component of Red Hat Enterprise Linux 9; edk2-tools as a component of Red Hat Enterprise Linux 9; edk2-tools-doc as a component of Red Hat Enterprise Linux 9; edk2.src as a component of Red Hat Enterprise Linux 9; shim-aa64 as a component of Red Hat Enterprise Linux 9; shim-unsigned-aarch64.src as a component of Red Hat Enterprise Linux 9; shim-unsigned-x64 as a component of Red Hat Enterprise Linux 9; and 4 more · Fixed: openssl-main@aarch64 as a component of Red Hat Hardened Images; openssl-main@src as a component of Red Hat Hardened Images; openssl-main@x86_64 as a component of Red Hat Hardened Images
    After
    edk2-aarch64 as a component of Red Hat Enterprise Linux 10; edk2-ovmf as a component of Red Hat Enterprise Linux 10; edk2-tools as a component of Red Hat Enterprise Linux 10; edk2-tools-doc as a component of Red Hat Enterprise Linux 10; edk2.src as a component of Red Hat Enterprise Linux 10; mokutil as a component of Red Hat Enterprise Linux 10; shim-aa64 as a component of Red Hat Enterprise Linux 10; shim-unsigned-aarch64.src as a component of Red Hat Enterprise Linux 10; shim-unsigned-x64.src as a component of Red Hat Enterprise Linux 10; shim-x64 as a component of Red Hat Enterprise Linux 10; AAVMF as a component of Red Hat Enterprise Linux 7; OVMF as a component of Red Hat Enterprise Linux 7; ovmf.src as a component of Red Hat Enterprise Linux 7; edk2-aarch64 as a component of Red Hat Enterprise Linux 8; edk2-ovmf as a component of Red Hat Enterprise Linux 8; edk2.src as a component of Red Hat Enterprise Linux 8; shim-aa64 as a component of Red Hat Enterprise Linux 8; shim-ia32 as a component of Red Hat Enterprise Linux 8; shim-unsigned-x64 as a component of Red Hat Enterprise Linux 8; shim-unsigned-x64.src as a component of Red Hat Enterprise Linux 8; shim-x64 as a component of Red Hat Enterprise Linux 8; shim.src as a component of Red Hat Enterprise Linux 8; edk2-aarch64 as a component of Red Hat Enterprise Linux 9; edk2-ovmf as a component of Red Hat Enterprise Linux 9; edk2-tools as a component of Red Hat Enterprise Linux 9; edk2-tools-doc as a component of Red Hat Enterprise Linux 9; edk2.src as a component of Red Hat Enterprise Linux 9; shim-aa64 as a component of Red Hat Enterprise Linux 9; shim-unsigned-aarch64.src as a component of Red Hat Enterprise Linux 9; shim-unsigned-x64 as a component of Red Hat Enterprise Linux 9; and 5 more · Fixed: openssl-main@aarch64 as a component of Red Hat Hardened Images; openssl-main@src as a component of Red Hat Hardened Images; openssl-main@x86_64 as a component of Red Hat Hardened Images
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-19958↗Red Hat Product Security security advisory↗CVE authority or vendor reference↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
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.
Free version - for non-commercial use only.CVE-2026-28386 · cve.blacktree.nl