Security readout for executives and security teams
Plain-English summary
Affected Erlang/OTP applications may trust a revoked certificate because OCSP validation fails to check whether the responder certificate has expired. Abuse requires possession of that expired responder certificate's private key. The main risks are accepting a revoked server certificate or, in some direct API uses, allowing authentication with a revoked client certificate.
Executive priority
Treat this as an accelerated maintenance item rather than a general emergency. Raise priority for internet-facing Erlang TLS clients using OCSP stapling and services using OCSP-backed client-certificate authentication. Exploitation prerequisites are substantial, but successful abuse could undermine certificate revocation and authentication controls.
Technical view
The pubkey_ocsp verification paths accept OCSP responses signed by an authorized but expired responder certificate without validating its notBefore and notAfter dates. A forged response can therefore make a revoked certificate appear valid. Relevant paths include TLS clients using OCSP stapling and applications calling public_key:pkix_ocsp_validate/5 directly.
Likely exposure
Exposure begins with OTP 27.0 and depends on the maintained branch. Fixed releases are OTP 27.3.4.12, 28.5.0.1, and 29.0.1, corresponding to public_key 1.17.1.3, 1.20.3.1, and 1.21.1. Systems not using OCSP stapling or direct OCSP validation are less likely to be affected.
Exploitation context
Exploitation requires the private key of an expired CA-designated OCSP responder certificate and a malicious or compromised server, or another suitable response-delivery position. The CVSS v4.0 score is 6.3 with high complexity and additional prerequisites. KEV is false, and the provided sources do not establish active exploitation.
Researcher notes
Impact depends on application behavior after successful OCSP validation. The source bundle describes limited integrity effects rather than confidentiality or availability impact. Its structured affected-package entries are less precise than the narrative branch information, so confirm exact version status against the vendor advisory and relevant patch commits.
Mitigation direction
- Upgrade to OTP 27.3.4.12, 28.5.0.1, or 29.0.1, as appropriate for the maintained release branch.
- Alternatively, update public_key to the corresponding fixed release supported by the deployed OTP branch.
- If immediate upgrading is unavailable, consult Erlang's advisory for supported guidance and reduce reliance on affected OCSP validation.
- Prioritize services using OCSP-backed client-certificate authentication or processing sensitive connections.
Validation and detection
- Inventory deployed Erlang/OTP and public_key versions, including bundled runtimes and containers.
- Identify TLS clients using OCSP stapling and applications calling public_key:pkix_ocsp_validate/5 directly.
- Confirm upgraded nodes report a fixed branch version and all affected services were restarted or redeployed.
- Test authorized staging systems to confirm OCSP responses using expired responder certificates are rejected.
- Review client-certificate authentication paths where accepting revoked credentials could grant access.
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
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CWE-295: Exact CWE lookup
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Open ATT&CK lookupCWE-672: Exact CWE lookup
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Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-42791 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
- Medium
- CVSS
- 6.3 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA: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:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N——EEFVulnerability scoring details
Base CVSS 4.0 score
6.3MediumVector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA: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
- https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fffCVE reference, EEF · vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-42791.htmlCVE reference, EEF · related
- https://osv.dev/vulnerability/EEF-CVE-2026-42791CVE reference, EEF · related
- https://www.erlang.org/doc/system/versions.html#order-of-versionsCVE reference, EEF · x_version-scheme
- https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169bCVE reference, EEF · patch
- https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76CVE reference, EEF · 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 Certificate Validation
Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Operation on a Resource after Expiration or Release
Operation on a Resource after Expiration or Release represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.