Threat Intelligence Database

In Mbed TLS 3.6.x before 3.6.7 and 4.1.x before 4.1.2, the TLS 1.3 client accepts HelloRetryRequest selecting an unadvertised group.

Mbed TLS versions from 3.3.0 up to 3.6.5 and 4.0.0 are affected by an algorithm downgrade vulnerability. This issue allows an attacker to force the use of weaker cryptographic algorithms during a TLS handshake. The vulnerability has a CVSS score of 6.5, indicating a medium severity level.

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HighVulnerabilityUnited StatesChinaGermany+9#cve#cve-2026-25835#gcve

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.

CVE-2026-34876 is an out-of-bounds read vulnerability in Mbed TLS 3.x before 3.6.6 affecting the multipart CCM API. The vulnerability arises from missing validation of the tag_len parameter in the mbedtls_ccm_finish() function, allowing attackers to read adjacent CCM context data. In Mbed TLS 4.x, the internal implementation has the same issue, but the vulnerable function is not exposed in the public API. Exploitation requires direct application-level use of the multipart CCM API with an oversized tag_len. This vulnerability has a high severity with a CVSS score of 7.5 and impacts confidentiality but not integrity or availability.

A critical vulnerability in Mbed TLS versions 3.5.0 through 4.0.0 allows remote attackers to impersonate clients during the resumption of a TLS 1.3 session. This flaw, classified as improper authentication (CWE-287), can be exploited without authentication or user interaction, impacting confidentiality and integrity. No official patch or remediation details are currently available. There are no known exploits in the wild at this time.

In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.

MediumVulnerabilityUnited StatesGermanyChina+7#cve#cve-2025-66442

CVE-2026-34871 is a vulnerability in Mbed TLS versions before 3.6.6 and 4.x before 4.1.0, as well as TF-PSA-Crypto before 1.1.0, involving a predictable seed in a pseudo-random number generator (PRNG). This weakness can compromise the confidentiality and integrity of cryptographic operations relying on the affected PRNG. The vulnerability has a medium severity with a CVSS score of 6.

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.

HighVulnerabilityUnited StatesChinaGermany+7#cve#cve-2026-34874

A buffer overflow vulnerability exists in the x509_inet_pton_ipv6() function of Mbed TLS versions 3.5.0 through 3.6.5. This issue was fixed in versions 3.6.6 and 4.1.0.