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CVE-2016-8671 Matrixssl CVE debrief

CVE-2016-8671 is a MatrixSSL vulnerability in the pstm_exptmod modular exponentiation function affecting MatrixSSL 3.8.6 and earlier. According to the CVE record, the bug could let remote attackers predict secret key material through unspecified vectors. The issue was described as the result of an incomplete fix for CVE-2016-6887, so organizations that patched only the earlier problem should verify they are on a version that includes the later correction.

Vendor
Matrixssl
Product
Unknown
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2017-01-13
Original CVE updated
2026-05-13
Advisory published
2017-01-13
Advisory updated
2026-05-13

Who should care

Teams that deploy MatrixSSL in embedded devices, network appliances, or any product that relies on MatrixSSL for TLS/cryptographic operations should prioritize review. Security and platform owners responsible for patching third-party crypto libraries should also check for downstream products that bundle MatrixSSL.

Technical summary

The NVD record maps CVE-2016-8671 to MatrixSSL versions up to and including 3.8.6. The affected code path is pstm_exptmod, which performs modular exponentiation. NVD assigns CVSS 3.0 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating a network-reachable issue with high confidentiality impact. The CVE description ties the flaw to an incomplete remediation of CVE-2016-6887, suggesting that earlier mitigation did not fully address the underlying cryptographic error.

Defensive priority

Medium. The vulnerability is remote-facing and confidentiality-impacting, but the CVSS complexity is high and the public record does not indicate active exploitation or KEV listing.

Recommended defensive actions

  • Identify whether MatrixSSL is used directly or bundled in vendor firmware/products.
  • Confirm that deployed MatrixSSL builds are newer than 3.8.6 and include the complete fix for CVE-2016-6887/CVE-2016-8671.
  • Prioritize updates in internet-facing products and devices that negotiate TLS with untrusted peers.
  • If patching is delayed, restrict exposure to trusted networks and monitor for unexpected TLS/cryptographic failures or vendor advisories.
  • Review downstream vendor security notices and firmware updates, since MatrixSSL is often embedded in third-party products.

Evidence notes

The CVE was published on 2017-01-13. NVD marks the record as modified on 2026-05-13, but the vulnerability timing should be treated from the CVE publication date, not the later modification date. NVD lists the affected CPE as MatrixSSL versions through 3.8.6 and provides the CVSS 3.0 vector AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N. References in the record include oss-security mailing list posts, a SecurityFocus entry, and a Fuzzing Project write-up describing the incomplete fix for CVE-2016-6887.

Sources and references

Verified primary and authoritative sources

  • CVE-2016-8671 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2016-8671

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2016-8671 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2016-8671

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://blog.fuzzing-project.org/54-Update-on-MatrixSSL-miscalculation-CVE-2016-8671%2C-incomplete-fix-for-CVE-2016-6887.html

    [email protected]

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.