CVE catalog
CVE-2026-34876
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 o
- Severity
- High · CVSS 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.39% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | mbedtls | sid | 3.6.7-3 | fixed |
| Debian | mbedtls | forky | 3.6.7-3 | fixed |
| Debian | mbedtls | trixie | 3.6.6-0.1~deb13u1 | fixed |
| Debian | mbedtls | bookworm | 2.28.3-1 | vulnerable |
| Cpe | mbedtls | Not reported | Not reported | vulnerable |
| Cpe | mbed_tls | Not reported | 3.6.6 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | mbedtls | source | sid | 3.6.6-0.1 | not yet assigned | Not reported | [1132577] |
| Debian | mbedtls | source | forky | 3.6.6-0.1 | not yet assigned | Not reported | [1132577] |
| Debian | mbedtls | source | trixie | 3.6.6-0.1~deb13u1 | not yet assigned | Not reported | [1132577] |
| Debian | mbedtls | source | bookworm | (unfixed) | not yet assigned | Not reported | [1132577] |
| Cpe | mbed_tls | cpe | Not reported | 3.6.6 | Not reported | Not reported | Not reported |
Notes
[bookworm] mbedtls: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [libmbedcrypto7]Affected
Source package: [mbedtls]
Details (2)
2.28.3-1· amd64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
2.28.3-1· arm64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- [libmbedtls14]Affected
Source package: [mbedtls]
Details (2)
2.28.3-1· amd64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
2.28.3-1· arm64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- [libmbedtls-dev]Affected
Source package: [mbedtls]
Details (2)
2.28.3-1· amd64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
2.28.3-1· arm64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- [libmbedtls-doc]Affected
Source package: [mbedtls]
Details (2)
2.28.3-1· all · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
2.28.3-1· all · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- [libmbedx509-1]Affected
Source package: [mbedtls]
Details (2)
2.28.3-1· amd64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
2.28.3-1· arm64 · bookwormAffected
nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
[Debian 13 (Trixie)]
- [libmbedcrypto16]Affected
Source package: [mbedtls]
Details (2)
3.6.5-0.1~deb13u1· amd64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
3.6.5-0.1~deb13u1· arm64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
- [libmbedtls21]Affected
Source package: [mbedtls]
Details (2)
3.6.5-0.1~deb13u1· amd64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
3.6.5-0.1~deb13u1· arm64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
- [libmbedtls-dev]Affected
Source package: [mbedtls]
Details (2)
3.6.5-0.1~deb13u1· amd64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
3.6.5-0.1~deb13u1· arm64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
- [libmbedtls-doc]Affected
Source package: [mbedtls]
Details (2)
3.6.5-0.1~deb13u1· all · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
3.6.5-0.1~deb13u1· all · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
- [libmbedx509-7]Affected
Source package: [mbedtls]
Details (2)
3.6.5-0.1~deb13u1· amd64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
3.6.5-0.1~deb13u1· arm64 · trixieAffected · Fixed:
3.6.6-0.1~deb13u1nvd · mbedtls · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_10498-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-34876]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-34876]
- [https://security-tracker.debian.org/tracker/CVE-2026-34876]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34876.json]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]