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CVE-2016-6129 Libtom CVE debrief

CVE-2016-6129 is a high-severity RSA signature verification flaw in LibTomCrypt’s rsa_verify_hash_ex function, used by OP-TEE before 2.2.0. The issue stems from missing validation that the message length matches the ASN.1 encoded data length, which can make RSA signature or certificate forgery easier for a remote attacker. NVD classifies the weakness as CWE-20 and rates it CVSS 3.0 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).

Vendor
Libtom
Product
CVE-2016-6129
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2017-02-13
Original CVE updated
2026-05-13
Advisory published
2017-02-13
Advisory updated
2026-05-13

Who should care

Organizations using OP-TEE, LibTomCrypt, or downstream products that depend on their RSA signature verification or certificate validation paths should prioritize this issue. Security teams should especially review embedded, trusted-execution, and authentication workflows that rely on these libraries for integrity decisions.

Technical summary

According to the supplied NVD description, the flaw is in rsa_verify_hash_ex in rsa_verify_hash.c. The function does not validate that the message length equals the ASN.1 encoded data length. That missing check weakens RSA signature verification and can allow a remote attacker to leverage a Bleichenbacher-style signature forgery attack. The supplied NVD record maps the weakness to CWE-20 and lists affected ranges up to OP-TEE OS 2.1.0 and LibTomCrypt 1.17.

Defensive priority

High. The impact is integrity-only but direct: successful exploitation can undermine trust decisions made by signature verification or certificate validation. Because the attack is network-reachable and requires no privileges or user interaction in the supplied CVSS vector, affected deployments should be treated as urgent upgrade candidates.

Recommended defensive actions

  • Upgrade OP-TEE to 2.2.0 or later if it is in use.
  • Upgrade LibTomCrypt beyond version 1.17 if it is used directly or through a downstream product.
  • Review any RSA-based verification or certificate validation code paths that depend on these libraries.
  • Confirm whether embedded or trusted-execution deployments vendor-patch this issue rather than relying on upstream version numbers alone.
  • Use the linked vendor and patch references to verify fixed builds and rollout guidance.

Evidence notes

The supplied corpus identifies the issue in the NVD record for CVE-2016-6129 and cites the original description, affected CPE criteria, CVSS vector, and CWE-20 mapping. References include a Red Hat Bugzilla issue, a LibTomCrypt commit labeled as a patch/third-party advisory, and the OP-TEE advisories page. Published date in the supplied record is 2017-02-13T18:59:00.660Z; modified date is 2026-05-13T00:24:29.033Z.

Official resources

The supplied official record shows CVE publication on 2017-02-13T18:59:00.660Z and a later modification on 2026-05-13T00:24:29.033Z. No separate vendor disclosure date is included in the supplied corpus.