CVE-2026-34877: arm mbed_tls Execution with Unnecessary Privileges
Vulnerability summary
CVE-2026-34877 is a critical (CVSS 9.8) Execution with Unnecessary Privileges vulnerability in arm mbed_tls. EPSS estimates a 0.73% chance of exploitation in the next 30 days, higher than 53.2% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 1 · Related 1Timeline
- 02-04-2026PublishedVulnerability first disclosed.
- 02-04-2026Last modifiedVulnerability information updated.
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 metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.73%
Chance of exploitation in the next 30 days
Percentile
53%
Versus all other CVEs
30-day change
+0.30 pp
From 0.43% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-250Execution with Unnecessary PrivilegesThe product performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses.
- CWE-502Deserialization of Untrusted DataThe product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
Affected systems
Arm1 product
- mbed_tls≥ 2.19.0, < 3.6.6
Debian1 product
- mbedtlsAll versions (No fix recorded) | < 3.6.6-0.1
Trustedfirmware1 product
- mbed_tls4.0.0
Ubuntu1 product
- mbedtlsAll versions (No fix recorded)
4 vendors · 4 products
References
5 links- mbed-tls.readthedocs.io/en/latest/security-advisories/Vendor Advisory
