CVE-2026-34872: arm mbed_tls
Vulnerability summary
CVE-2026-34872 is a critical (CVSS 9.1) vulnerability in arm mbed_tls. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 18.8% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 1 · Related 1Timeline
- 01-04-2026PublishedVulnerability first disclosed.
- 01-04-2026Last modifiedVulnerability information updated.
Description
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).
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- OSV · DebianEcosystem advisory · calculated9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- NVDNIST9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS trend
Probability
0.28%
Chance of exploitation in the next 30 days
Percentile
19%
Versus all other CVEs
30-day change
+0.07 pp
From 0.20% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Arm2 products
- mbed_tls< 3.6.6
- tf-psa-crypto1.0.0
Debian1 product
- mbedtlsAll versions (No fix recorded) | < 3.6.6-0.1~deb13u1 | < 3.6.6-0.1
Ubuntu1 product
- mbedtlsAll versions (No fix recorded)
3 vendors · 4 products
