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Fencer Vulns
medium 6.5

CVE-2026-25834 json

Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade.

published 2026-04-01 7 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-17967

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade.

Patch / fix

  • trustedfirmware mbed_tls 3.6.6
  • mbedtls Debian 13 3.6.6-0.1~deb13u1
  • mbedtls Debian 14 3.6.6-0.1

debian advisories DEBIAN-CVE-2026-25834

  • ovmf SLES for SAP applications 16.0, SLES 16.0 202502-160000.5.1

suse advisories SUSE-SU-2026:22016-1

  • mbedtls openSUSE Leap 16.0 3.6.6-bp160.1.1
  • mbedtls openSUSE Tumbleweed 3.6.6-1.1

opensuse advisories openSUSE-SU-2026:21144-1openSUSE-SU-2026:10498-1

  • mbedtls Alpine 3.24, Alpine 3.23, Alpine 3.22 +2 more 3.6.6-r0
  • mbedtls3 Alpine 3.24 3.6.6-r0

alpine advisories ALPINE-CVE-2026-25834

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-25834 updated cvss 6.5

mbedtls: Mbed TLS: Algorithm downgrade vulnerability

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Classification

Weakness
  • CWE-295 Improper Certificate Validation
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.