CVE-2026-34876
An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in...
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
7.5
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.
- Record
CVE-2026-34876- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-125
- Updated
- 2026-11-02
EUVDEUVD-2026-18356
7.5
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.
- Record
EUVD-2026-18356- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-jw9g-6hxw-4whq
7.5
An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in...
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.
- Record
GHSA-jw9g-6hxw-4whq- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-125
- Updated
- 2026-11-02
NVD
7.5
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.
- Record
CVE-2026-34876- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-125
- Updated
- 2026-11-02
OSV
7.5
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.
- Record
CVE-2026-34876- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-34876
7.5
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.
- Record
DEBIAN-CVE-2026-34876- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-34876
7.5
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.
- Record
UBUNTU-CVE-2026-34876- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVopenSUSE-SU-2026:10498-1 No score
libeverest-3.6.6-1.1 on GA media
These are all security issues fixed in the libeverest-3.6.6-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:10498-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
mbedtlsDebian:12 |
All versions, plus listed versions 2.28.3-12.28.4-12.28.5-12.28.6-12.28.7-1 Show 18 moreShow less2.28.7-1.12.28.7-1.1~exp12.28.8-13.6.0-13.6.0-23.6.0-33.6.2-13.6.2-23.6.2-33.6.3-13.6.4-13.6.4-23.6.5-0.13.6.5-0.1~deb13u13.6.6-0.13.6.6-0.1~deb13u13.6.7-23.6.7-3 |
None known |
mbedtlsDebian:13 |
before 3.6.6-0.1~deb13u1, plus listed versions 3.6.4-23.6.5-0.13.6.5-0.1~deb13u1 |
3.6.6-0.1~deb13u1 |
mbedtlsDebian:14 |
before 3.6.6-0.1, plus listed versions 3.6.4-23.6.5-0.13.6.5-0.1~deb13u13.6.6-0.1~deb13u1 |
3.6.6-0.1 |
mbedtlsUbuntu:16.04:LTS |
All versions, plus listed versions 2.1.2-12.2.0-12.2.1-12.2.1-22.2.1-2ubuntu0.12.2.1-2ubuntu0.22.2.1-2ubuntu0.3 |
None known |
mbedtlsUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 2.5.1-1ubuntu12.6.0-12.7.0-22.8.0-12.8.0-1ubuntu0.1~esm1 |
None known |
mbedtlsUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 2.16.2-12.16.3-12.16.4-1ubuntu22.16.4-1ubuntu2+esm1 |
None known |
mbedtlsUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 2.16.9-0.1ubuntu12.16.11-0.1ubuntu12.16.11-0.32.28.0-12.28.0-1build12.28.0-1ubuntu0.1~esm1 |
None known |
mbedtlsUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 2.28.3-12.28.6-1ubuntu12.28.7-1ubuntu12.28.7-1.1ubuntu12.28.8-12.28.8-1ubuntu0.1~esm1 |
None known |
mbedtlsUbuntu:25.10 |
All versions, plus listed versions 3.6.2-3ubuntu1 |
None known |
mbedtlsUbuntu:26.10 |
All versions, plus listed versions 3.6.5-0.1ubuntu23.6.6-0.1ubuntu13.6.7-3ubuntu1 |
None known |
mbedtlsUbuntu:26.04:LTS |
All versions, plus listed versions 3.6.2-3ubuntu13.6.5-0.1ubuntu13.6.5-0.1ubuntu2 |
None known |
mbedtlsopenSUSE:Tumbleweed From an advisory covering 10 CVEs |
before 3.6.6-1.1 | 3.6.6-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-34876 is a high vulnerability (CVSS 7.5) in Trustedfirmware Mbed Tls, published April 2, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in mbedtls 3.6.6-0.1~deb13u1.
References
mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories
mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check
nvd.nist.gov/vuln/detail/CVE-2026-34876
github.com/advisories/GHSA-jw9g-6hxw-4whq
github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34876.json
security-tracker.debian.org/tracker/CVE-2026-34876
Show 12 moreShow less
ubuntu.com/security/CVE-2026-34876
cve.org/CVERecord?id=CVE-2026-34876
suse.com/security/cve/CVE-2026-25833
suse.com/security/cve/CVE-2026-25834
suse.com/security/cve/CVE-2026-25835
suse.com/security/cve/CVE-2026-34871
suse.com/security/cve/CVE-2026-34872
suse.com/security/cve/CVE-2026-34873
suse.com/security/cve/CVE-2026-34874
suse.com/security/cve/CVE-2026-34875
suse.com/security/cve/CVE-2026-34876
suse.com/security/cve/CVE-2026-34877