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Fencer Vulns
critical 9.1

CVE-2026-28386 in the critical feed json

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

published 2026-04-07 7 mo ago modified 2026-07-24 3 mo ago also EUVD-2026-19958

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

Issue 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.

Patch / fix

  • OpenSSL OpenSSL 3.6.2
  • openssl Debian 14 3.6.2-1

debian advisories DEBIAN-CVE-2026-28386

  • openssl hummingbird 1 3.5.6-0.1.hum1
  • openssl-libs hummingbird 1 3.5.6-0.1.hum1
  • openssl-perl hummingbird 1 3.5.6-0.1.hum1
  • openssl-config-fips hummingbird 1 3.5.6-0.1.hum1
  • openssl-devel-engine hummingbird 1 3.5.6-0.1.hum1

red hat advisories RHSA-2026:7261

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28386 updated cvss 5.9

openssl: openssl: Denial of Service due to out-of-bounds read in AES-CFB128

  • Red Hat Enterprise Linux 7 ovmf, OVMF, AAVMF Red Hat Enterprise Linux 8 edk2, shim, shim-x64, edk2-ovmf, shim-aa64, shim-ia32, +2 more Red Hat Enterprise Linux 9 edk2, shim, shim-x64, edk2-ovmf, shim-aa64, edk2-tools, +3 more Red Hat Enterprise Linux 10 edk2, shim, shim-unsigned-x64, shim-unsigned-aarch64 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Hardened Images openssl 3.5.6-0.1.hum1, openssl-libs 3.5.6-0.1.hum1, openssl-perl 3.5.6-0.1.hum1, openssl-config-fips 3.5.6-0.1.hum1, openssl-devel-engine 3.5.6-0.1.hum1
    fixed: vendor fix RHSA-2026:7261
  • Red Hat Enterprise Linux 6 openssl, openssl-perl Red Hat Enterprise Linux 7 openssl, openssl-libs, openssl-perl
    not affected: vulnerable code not present
  • Red Hat Enterprise Linux 8 openssl, openssl-libs, openssl-perl, mingw-openssl, mingw32-openssl, mingw64-openssl, +1 more
    not affected: component not present
  • Red Hat Enterprise Linux 9 openssl, openssl-libs, openssl-perl, compat-openssl11 Red Hat Enterprise Linux 10 openssl Red Hat JBoss Core Services openssl
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected products

  • OpenSSL OpenSSL

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.