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.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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Fixes
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Workaround
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References
History
Thu, 02 Apr 2026 15:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| References |
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Projects
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MITRE
Status: PUBLISHED
Assigner: mitre
Published:
Updated: 2026-04-02T15:54:45.230Z
Reserved: 2026-03-31T00:00:00.000Z
Link: CVE-2026-34876
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
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Weaknesses
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