CVE-2026-34877: Mbed TLS · CVE-2026-34877 is a critical
Source CVE Database V5
Not known to be exploited · CVSS 9.8 Critical.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 2 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
AI-suggested
Until a fix is available, avoid using vulnerable versions or restrict access to serialized SSL context/session structures to trusted parties only.
Description
CVE-2026-34877 is a critical vulnerability in Mbed TLS versions from 2.19.0 up to 3.6.5 and version 4.0.0. It involves insufficient protection of serialized SSL context or session structures, which allows an attacker who can modify these serialized structures to cause memory corruption and potentially execute arbitrary code. The vulnerability stems from incorrect use of privileged APIs. The CVSS score is 9.