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VulnerabilityPublished

CVE-2026-34877: Mbed TLS · CVE-2026-34877 is a critical

Source CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

References

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