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Fencer Vulns
high 8.2

CVE-2026-77214 json

libexpat Heap Buffer Over-read in xmlparse.c via XML_ParseBuffer

published 2026-10-07 33 d ago modified 2026-11-08 25 h ago also EUVD-2026-94368

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

libexpat before commit 13c5f63 contains a heap buffer over-read vulnerability in xmlparse.c. XML_ParseBuffer advances the parse buffer end with parser->m_bufferEnd += len using a caller-supplied length that is not validated against the allocated buffer size, so repeated XML_ParseBuffer calls move m_bufferEnd past the end of the heap allocation and subsequent parsing reads out of bounds. Reaching this path requires a parse buffer to already be present; otherwise XML_ParseBuffer returns XML_ERROR_NO_BUFFER. A buffer is present after a prior call to XML_GetBuffer, either directly (the common case) or indirectly through a prior XML_Parse call that allocates the buffer internally. The over-read discloses adjacent heap memory to the calling application, recovering heap pointers, libc function pointers, and code pointers sufficient to defeat ASLR and build further exploitation primitives.

Patch / fix

  • libexpat_project libexpat 2.9.0
  • expat Debian 12 2.5.0-1+deb12u5
  • expat Debian 13 2.9.0-1~deb13u1
  • expat Debian 14 2.9.0-1

debian advisories DEBIAN-CVE-2026-77214

  • expat hummingbird 1 2.8.5-1.2.hum1

red hat advisories RHSA-2026:77959

  • expat SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2.8.5-160000.1.1
  • expat Linux Micro 6.1 2.8.5-slfo.1.1_1.1
  • expat SLE Module for Basesystem 15 SP7 2.8.5-150700.3.15.1
  • expat Linux Micro 6.0 2.8.5-159998.1.1
  • expat SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +10 more 2.8.5-150400.3.40.1
  • expat SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 2.8.5-21.55.1

suse advisories SUSE-SU-2026:24460-1SUSE-SU-2026:24469-1SUSE-SU-2026:24554-1SUSE-SU-2026:4619-1SUSE-SU-2026:24323-1SUSE-SU-2026:4623-1

  • expat openSUSE Leap 16.0 2.8.5-160000.1.1
  • expat openSUSE Tumbleweed 2.9.0-1.1

opensuse advisories openSUSE-SU-2026:22177-1openSUSE-SU-2026:12100-1

  • expat AlmaLinux 8 2.5.0-6.el8_10
  • firefox AlmaLinux 10 153.5.0-1.el10_2
  • expat AlmaLinux 9 2.5.0-6.el9_8.7
  • expat AlmaLinux 10 2.7.3-1.el10_2.7

almalinux advisories ALSA-2026:92323ALSA-2026:89758ALSA-2026:88247ALSA-2026:88248

  • firefox Rocky Linux 10 153.5.0-1.el10_2
  • expat Rocky Linux 8 2.5.0-6.el8_10
  • expat Rocky Linux 10 2.7.3-1.el10_2.7
  • expat Rocky Linux 9 2.5.0-6.el9_8.7

rocky linux advisories RLSA-2026:89758RLSA-2026:92323RLSA-2026:88248RLSA-2026:88247

  • expat Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 2.9.0-r0

alpine advisories ALPINE-CVE-2026-77214

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • expat Azure Linux 3.0 2.9.0-1

azure linux advisories AZL-106728

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-77214 updated cvss 8.2

expat: expat: Information disclosure via heap buffer over-read in XML_ParseBuffer

  • Red Hat Enterprise Linux 6 expat, compat-expat1
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 7 expat, firefox Red Hat Enterprise Linux 8 firefox, xmlrpc-c, mingw-expat, thunderbird, xmlrpc-c-c++, mingw32-expat, +4 more Red Hat Enterprise Linux 9 firefox, firefox-x11, thunderbird, thunderbird 140.14.0-1.el10_2 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: no fix available
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-dashboard-rhel9
    under investigation
  • Red Hat Cost Management On-Premise 1 costmanagement/costmanagement-ui-rhel10 1793825318
    fixed: vendor fix RHSA-2026:95365
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1793733716, discovery/discovery-server-rhel9 1793734080
    fixed: vendor fix RHSA-2026:94802
  • Red Hat Enterprise Linux AppStream (v. 9) expat-devel 2.5.0-6.el9_8.7, expat-debuginfo 2.5.0-6.el9_8.7, expat-debugsource 2.5.0-6.el9_8.7
    fixed: vendor fix RHSA-2026:88247
  • Red Hat Enterprise Linux AppStream (v. 10) firefox 153.5.0-1.el10_2
    fixed: vendor fix RHSA-2026:88248
  • Red Hat Enterprise Linux BaseOS (v. 8) expat 2.5.0-6.el8_10
    fixed: vendor fix RHSA-2026:92323
show 7 more
  • Red Hat Enterprise Linux BaseOS (v. 9) expat 2.5.0-6.el9_8.7
    fixed: vendor fix RHSA-2026:88247
  • Red Hat Enterprise Linux BaseOS (v. 10) expat 2.7.3-1.el10_2.7
    fixed: vendor fix RHSA-2026:88248
  • Red Hat Hardened Images expat 2.9.0-1.hum1, expat 2.8.5-1.2.hum1
    fixed: vendor fix RHSA-2026:77959
  • Red Hat OpenShift Container Platform 4.22 rhcos 4.22.9.8.202611032353
    fixed: vendor fix RHSA-2026:95346
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1793005764, rhui5/rhua-rhel9 1793005812, rhui5/haproxy-rhel9 1793004999, rhui5/installer-rhel9 1793004989, rhui5/cds-kubernetes-rhel9 1793005771
    fixed: vendor fix RHSA-2026:89907
  • Red Hat Enterprise Linux 10 thunderbird 140.14.0-1.el10_2
    not affected: vulnerable code not in execute path
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9
    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
30 d ago

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 8.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N
CNA 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L
CNA 4.0 8.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • libexpat libexpat

Classification

Weakness

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.