An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to improper input validation. Using finite-field Diffie-Hellman, the other party can force the shared secret into a small set of values (lack of contributory behavior). This is a problem for protocols that depend on contributory behavior (which is not the case for TLS). The attack can be carried by the peer, or depending on the protocol by an active network attacker (person in the middle).
CVE-2026-34872
Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-01. NVD baseline CVSS 9.1; sources differ by 0.0.
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.1
- EG Score
- 9.1(medium)
- EG Risk
- 56(Track)EG Risk 56/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity91% × 45%Exploitation0% × 40%Automatability100% × 15%Action: Routine — remediate on your standard cadence. - EPSS
- 10.6%
- KEV
- Not listed
Published
April 1, 2026
Last Modified
April 3, 2026
Advisory Details (2)
Auto-updated May 20, 2026FFDH: lack of contributory behaviour due to improper input validation (CVE-2026-34872) — Mbed TLS documentation
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/Security Advisories — Mbed TLS documentation
https://mbed-tls.readthedocs.io/en/latest/security-advisories/Vendor Advisories for CVE-2026-34872(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 37× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
Showing the most recent 100 of 108 total refreshes for this CVE.
- 2026-07-23 14:18 UTCEPSS rescore
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Related CVEs(same CWE)
Same CWE
10 shownCWE-347
Frequently asked(5)
What is CVE-2026-34872?
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What is the CVSS score of CVE-2026-34872?
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Dependency Blast Radius
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