CVE-2026-34876 Information disclosure in n/a
Attackers can read adjacent memory via oversized tag_len in Mbed TLS CCM API, potentially exposing sensitive context data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-34876?
CVE-2026-34876 is a high-severity vulnerability in n/a, published on 2 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.
Weakness: CWE-125
Which versions are affected by CVE-2026-34876?
It affects 1 product.
Products include Trustedfirmware Mbed Tls.
How do I fix CVE-2026-34876?
Upgrade to a fixed version.
Is CVE-2026-34876 being exploited?
There is no known exploitation of CVE-2026-34876 in the wild and no public exploit code.
Other vulnerabilities in n/a
Sources
Also known as DEBIAN-CVE-2026-34876, ECHO-2b14-d1fe-8a7a, GHSA-jw9g-6hxw-4whq, UBUNTU-CVE-2026-34876.