CVE-2026-28386

NameCVE-2026-28386
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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
openssl (PTS)bullseye1.1.1w-0+deb11u1fixed
bullseye (security)1.1.1w-0+deb11u5fixed
bookworm3.0.18-1~deb12u1fixed
bookworm (security)3.0.19-1~deb12u2fixed
trixie3.5.5-1~deb13u1fixed
trixie (security)3.5.5-1~deb13u2fixed
forky, sid3.6.2-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
opensslsourcebullseye(not affected)
opensslsourcebookworm(not affected)
opensslsourcetrixie(not affected)
opensslsource(unstable)3.6.2-1

Notes

[trixie] - openssl <not-affected> (Vulnerable code introduced later)
[bookworm] - openssl <not-affected> (Vulnerable code introduced later)
[bullseye] - openssl <not-affected> (Vulnerable code introduced later)
https://openssl-library.org/news/secadv/20260407.txt

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