[Debian-iot-maintainers] Bug#1132577: mbedtls: CVE-2026-34871 CVE-2026-34872 CVE-2026-34873 CVE-2026-34874 CVE-2026-34875 CVE-2026-34876 CVE-2026-34877

[Salvatore Bonaccorso]

Source: mbedtls
Version: 3.6.5-0.1
Severity: grave
Tags: security upstream
Justification: user security hole
X-Debbugs-Cc: carnil at debian.org, Debian Security Team <team at security.debian.org>

Hi,

The following vulnerabilities were published for mbedtls.

CVE-2026-34871[0]:
| An issue was discovered in Mbed TLS before 3.6.6 and 4.x before
| 4.1.0 and TF-PSA-Crypto before 1.1.0. There is a Predictable Seed in
| a Pseudo-Random Number Generator (PRNG).


CVE-2026-34872[1]:
| An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5
| and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in
| FFDH due to improper input validation. Using finite-field Diffie-
| Hellman, the other party can force the shared secret into a small
| set of values (lack of contributory behavior). This is a problem for
| protocols that depend on contributory behavior (which is not the
| case for TLS). The attack can be carried by the peer, or depending
| on the protocol by an active network attacker (person in the
| middle).


CVE-2026-34873[2]:
| An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client
| impersonation can occur while resuming a TLS 1.3 session.


CVE-2026-34874[3]:
| An issue was discovered in Mbed TLS through 3.6.5 and 4.x through
| 4.0.0. There is a NULL pointer dereference in distinguished name
| parsing that allows an attacker to write to address 0.


CVE-2026-34875[4]:
| An issue was discovered in Mbed TLS through 3.6.5 and TF-PSA-Crypto
| 1.0.0. A buffer overflow can occur in public key export for FFDH
| keys.


CVE-2026-34876[5]:
| 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.


CVE-2026-34877[6]:
| 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.


If you fix the vulnerabilities please also make sure to include the
CVE (Common Vulnerabilities & Exposures) ids in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-34871
    https://www.cve.org/CVERecord?id=CVE-2026-34871
[1] https://security-tracker.debian.org/tracker/CVE-2026-34872
    https://www.cve.org/CVERecord?id=CVE-2026-34872
[2] https://security-tracker.debian.org/tracker/CVE-2026-34873
    https://www.cve.org/CVERecord?id=CVE-2026-34873
[3] https://security-tracker.debian.org/tracker/CVE-2026-34874
    https://www.cve.org/CVERecord?id=CVE-2026-34874
[4] https://security-tracker.debian.org/tracker/CVE-2026-34875
    https://www.cve.org/CVERecord?id=CVE-2026-34875
[5] https://security-tracker.debian.org/tracker/CVE-2026-34876
    https://www.cve.org/CVERecord?id=CVE-2026-34876
[6] https://security-tracker.debian.org/tracker/CVE-2026-34877
    https://www.cve.org/CVERecord?id=CVE-2026-34877

Regards,
Salvatore