Security readout for executives and security teams
Plain-English summary
A flaw in specific OpenSSL authenticated-decryption paths can make a forged, empty encrypted message appear authentic. Systems could trust attacker-controlled messages when using EVP_Cipher() with ChaCha20-Poly1305 or AES-OCB and relying on its success result. Severity is critical, but exposure depends on this narrow application pattern.
Executive priority
Treat as urgent for exposed applications, while using code-path validation to avoid indiscriminate emergency changes. Immediately inventory affected OpenSSL use, prioritize remotely reachable message-processing systems, and deploy the appropriate vendor patch after focused testing.
Technical view
During EVP_Cipher() decryption, ChaCha20-Poly1305 and AES-OCB skip AEAD tag verification when ciphertext is empty, yet can return success. This is CWE-354. The CVSS 3.1 score is 9.1, with high confidentiality and integrity impact and no scored availability impact.
Likely exposure
Potential exposure requires an identified OpenSSL version, one of the two affected algorithms, attacker-influenced empty ciphertext, and EVP_Cipher()-based tag validation. The bundle identifies versions 4.0.0, 3.6.0, 3.5.0, 3.4.0, and 3.0.0. Listed FIPS modules are unaffected because these algorithms are not implemented there.
Exploitation context
CISA KEV status is false, and the supplied sources do not report active exploitation. The network-accessible CVSS vector indicates potential remote abuse where applications expose the vulnerable data path. The bundle provides no evidence about exploit prevalence, public proof-of-concept availability, or affected-application prevalence.
Researcher notes
The failure is specific to empty-ciphertext decryption finalized through EVP_Cipher(); ordinary non-empty ciphertext is not described as affected. The FIPS modules listed in the advisory are unaffected. The supplied version data does not fully define every affected patch-level range, so confirm exact package status with OpenSSL or downstream vendors.
Mitigation direction
- Apply the cited branch patch corresponding to 4.0.2, 3.6.4, 3.5.8, 3.4.7, or 3.0.22.
- Follow the OpenSSL advisory and downstream vendor guidance for supported upgrade packages.
- Until patched, reject empty ciphertext before affected EVP_Cipher() AEAD decryption paths.
- Prioritize externally reachable services that process untrusted authenticated-encryption messages.
Validation and detection
- Inventory runtime and statically linked OpenSSL versions, including application-bundled copies.
- Identify EVP_Cipher() decryption using ChaCha20-Poly1305 or AES-OCB.
- Determine whether untrusted inputs can supply empty ciphertext and an authentication tag.
- Regression-test that invalid tags with empty ciphertext are rejected after remediation.
- Verify deployed artifacts contain the appropriate cited patch or vendor-fixed release.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-354: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-75803 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N3.95.2CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- OpenSSL AdvisoryCVE reference, openssl · vendor-advisory
- 4.0.2 git commitCVE reference, openssl · patch
- 3.6.4 git commitCVE reference, openssl · patch
- 3.5.8 git commitCVE reference, openssl · patch
- 3.4.7 git commitCVE reference, openssl · patch
- 3.0.22 git commitCVE reference, openssl · patch
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Validation of Integrity Check Value
Improper Validation of Integrity Check Value represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.