CriticalCVE-2026-75803

    AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher() (CVE-2026-75803)

    Published Last modified Sources: Red Hat, Debian, Ubuntu, SUSE, Debian LTS, BSI, CVE.org

    What is affected, what to do

    A flaw in OpenSSL causes EVP_Cipher() to skip AEAD tag verification for ChaCha20-Poly1305 and AES-OCB ciphers when decrypting empty ciphertexts. This allows remote attackers to submit forged messages that affected applications incorrectly accept as valid.

    Update OpenSSL to version 4.0.2, OpenSSL to version 3.6.4, OpenSSL to version 3.5.8.

    Affected
    • OpenSSL lt 4.0.0..4.0.2
    • OpenSSL lt 3.6.0..3.6.4
    • OpenSSL lt 3.5.0..3.5.8
    • OpenSSL lt 3.4.0..3.4.7
    • OpenSSL lt 3.0.0..3.0.22
    Fixed in
    • OpenSSL 4.0.2
    • OpenSSL 3.6.4
    • OpenSSL 3.5.8
    • OpenSSL 3.4.7
    • OpenSSL 3.0.22

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v3

    9.1

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: Red Hat, Debian, Ubuntu, SUSE, Debian LTS, BSI, CVE.org

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 17.0

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    71.86 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.1
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.3 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    17.0
    Elevated — this CVE ranks above at least 10% of all CVEs scored today.
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 1 September 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-354

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A flaw in OpenSSL causes EVP_Cipher() to skip AEAD tag verification for ChaCha20-Poly1305 and AES-OCB ciphers when decrypting empty ciphertexts. This allows remote attackers to submit forged messages that affected applications incorrectly accept as valid.

    Source: redhat_csaf, Debian Security Advisories, Ubuntu Security Notices, suse_csaf, Debian LTS Advisories, BSI WID Portal, BSI CSAF, NVD (NIST), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    OpenSSLOpenSSL
    • 3.6.0 – < 3.6.4
    • 3.4.0 – < 3.4.7
    • 4.0.0 – < 4.0.2
    • 3.5.0 – < 3.5.8
    • 3.0.0 – < 3.0.22
    • 3.6.4
    • 3.4.7
    • 4.0.2
    • 3.5.8
    • 3.0.22
    opensslopenssl
    • 3.5.0 – < 3.5.8
    • 3.4.0 – < 3.4.7
    • 4.0.0 – < 4.0.2
    • 3.6.0 – < 3.6.4
    • 3.0.0 – < 3.0.22
    • 3.5.8
    • 3.4.7
    • 4.0.2
    • 3.6.4
    • 3.0.22
    MeinbergLANTIME
    • < V7.10.016
    • V7.10.016
    Open SourceOpenSSL
    • < 3.4.7
    • < 4.0.2
    • < 3.5.8
    • < 3.6.4
    • < 3.0.22
    • < 1.1.1zi
    • < 1.0.2zr
    • 3.4.7
    • 4.0.2
    • 3.5.8
    • 3.6.4
    • 3.0.22
    • 1.1.1zi
    • 1.0.2zr
    OracleDatabase Server
    • 23.4.0-23.26.3
    • 19.3-19.32
    • 21.3-21.23
    • —
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianopensslbookworm
    Linuxdebianopenssltrixie
    Linuxubuntuopenssljammy
    Linuxubuntuopensslnoble
    Linuxubuntuopensslresolute

    Weakness classes (CWE)

    • CWE-354Improper Validation of Integrity Check Value

      Base

      The product does not validate or incorrectly validates the integrity check values or "checksums" of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission.

      Entry at MITRE CWE-354

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Initial analysis by NVDNVD

      Newly listed as affected:
      • OpenSSL (3.5.0 – before 3.5.8; 3.6.0 – before 3.6.4; 4.0.0 – before 4.0.2; 3.4.0 – before 3.4.7; 3.0.0 – before 3.0.22)
      Show 7 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.5.8 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.4 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 4.0.0 up to (excluding) 4.0.2 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.4.0 up to (excluding) 3.4.7 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.22
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/119ab9555dc62275bbd71f6f49529b1a44feba42 Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/3621257986e27e540bf96a11570929a6e5a9e05b Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/6c7aa6f8f6449b7fe0137ee8be65fcd239bd7d6a Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/bdeb0cd994d915342787f117ee75044f0dc36f34 Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/bf95f5f772e9362f87b25cfa2f8cb15d984865b9 Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260825.txt Types: Vendor Advisory

      Source identifier: nvd@nist.gov

    2. Record modifiedopenssl.org

      Show 12 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/119ab9555dc62275bbd71f6f49529b1a44feba42
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/3621257986e27e540bf96a11570929a6e5a9e05b
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/6c7aa6f8f6449b7fe0137ee8be65fcd239bd7d6a
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/bdeb0cd994d915342787f117ee75044f0dc36f34
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/bf95f5f772e9362f87b25cfa2f8cb15d984865b9
      Referenceadded
      —
      https://openssl-library.org/news/secadv/20260825.txt
      Referenceremoved
      https://github.com/openssl/openssl/commit/119ab9555dc62275bbd71f6f49529b1a44feba42
      —
      Referenceremoved
      https://github.com/openssl/openssl/commit/3621257986e27e540bf96a11570929a6e5a9e05b
      —
      Referenceremoved
      https://github.com/openssl/openssl/commit/6c7aa6f8f6449b7fe0137ee8be65fcd239bd7d6a
      —
      Referenceremoved
      https://github.com/openssl/openssl/commit/bdeb0cd994d915342787f117ee75044f0dc36f34
      —
      Referenceremoved
      https://github.com/openssl/openssl/commit/bf95f5f772e9362f87b25cfa2f8cb15d984865b9
      —
      Referenceremoved
      https://openssl-library.org/news/secadv/20260825.txt
      —

      Source identifier: openssl-security@openssl.org

    3. Record modifiedCISA ADP

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
      SSVC assessmentadded
      —
      {"id":"CVE-2026-75803","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-01T18:22:51.167833Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    4. Receivedopenssl.org

      Weakness type: CWE-354

      Description added or changed

      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      OpenSSL
      Descriptionadded
      —
      Issue summary: ChaCha20-Poly1305 and AES-OCB decryption with an empty ciphertext can report success without verifying the supplied authentication tag when the operation is finalized by calling the EVP_Cipher() function. Impact summary: Applications calling EVP_Cipher() on an empty ciphertext and expecting the call to check the AEAD tag may accept forged messages. CWE: CWE-354 (Improper Validation of Integrity Check Value) Description: The EVP_Cipher() API call for AEAD ciphers behaves like a one shot encryption and decryption call. It also verifies the AEAD tag after the decryption operation. However for AES-OCB and ChaCha20-Poly1305 ciphers it skipped the AEAD tag verification when an empty ciphertext was passed to the function. The callers of this function might believe that a successful return indicates a valid AEAD tag for these ciphers, even when that has not truly been validated in this case. FIPS impact: no The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this CVE as the affected algorithms are not FIPS approved and thus not implemented in the FIPS module.
      Weakness type (CWE)added
      —
      CWE-354
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/119ab9555dc62275bbd71f6f49529b1a44feba42
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/3621257986e27e540bf96a11570929a6e5a9e05b
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/6c7aa6f8f6449b7fe0137ee8be65fcd239bd7d6a
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/bdeb0cd994d915342787f117ee75044f0dc36f34
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/bf95f5f772e9362f87b25cfa2f8cb15d984865b9
      Referenceadded
      —
      https://openssl-library.org/news/secadv/20260825.txt

      Source identifier: openssl-security@openssl.org

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