Critical severity · published Apr 2, 2026
CVE-2026-34877
An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0
9.8
CVSS
0.4%
EPSS
No
On KEV
Description
An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of serialized SSL context or session structures allows an attacker who can modify the serialized structures to induce memory corruption, leading to arbitrary code execution. This is caused by Incorrect Use of Privileged APIs.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 37% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MT
Mbed Tls · Arm
2.19.0 before 3.6.6 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34877
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-34877
Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/security-advisories/
Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-serialized-data/
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