Out-of-bounds Read in AES-CFB-128 on X86-64 with AVX-512 Support

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Summary

CVECVE-2026-28386
StatePUBLISHED
Assigneropenssl
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-07 22:16:20 UTC
Updated2026-04-08 21:27:00 UTC
DescriptionIssue summary: Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support can trigger an out-of-bounds read of up to 15 bytes when processing partial cipher blocks. Impact summary: This out-of-bounds read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not written to output. The vulnerable code path is only reached when processing partial blocks (when a previous call left an incomplete block and the current call provides fewer bytes than needed to complete it). Additionally, the input buffer must be positioned at a page boundary with the following page unmapped. CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or ChaCha20-Poly1305 instead. For these reasons the issue was assessed as Low severity according to our Security Policy. Only x86-64 systems with AVX-512 and VAES instruction support are affected. Other architectures and systems without VAES support use different code paths that are not affected. OpenSSL FIPS module in 3.6 version is affected by this issue.

Risk And Classification

EPSS: 0.000190000 probability, percentile 0.050600000 (date 2026-04-09)

Problem Types: CWE-125 | CWE-125 CWE-125 Out-of-bounds Read

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA OpenSSL OpenSSL affected 3.6.0 3.6.2 semver Not specified

References

ReferenceSourceLinkTags
openssl-library.org/news/secadv/20260407.txt [email protected] openssl-library.org
github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Stanislav Fort (Aisle Research) (en)

CNA: Pavel Kohout (Aisle Research) (en)

CNA: Alex Gaynor (Anthropic) (en)

CNA: Stanislav Fort (Aisle Research) (en)

CNA: Pavel Kohout (Aisle Research) (en)

CNA: Alex Gaynor (Anthropic) (en)

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