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Full vulnerability report · 2026
CVE-2026-56131High confidence

libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation

libexpat project · libexpat

4.9MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.18% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs libexpat project libexpat and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Alpine, Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

15 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Alpine v3.23v3.23 · mainexpatVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.2.8.2-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.22v3.22 · mainexpatVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.2.8.2-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.21v3.21 · mainexpatVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.2.8.2-r0Alpine Security Database ↗Source updated 3 Oct 2026
Debian trixietrixie · sourceexpatVendor fix publishedDebian records a fixed source-package version for this release.2.8.2-1~deb13u1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourceexpatVendor fix publishedDebian records a fixed source-package version for this release.2.5.0-1+deb12u3Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourceexpatVendor fix publishedDebian records a fixed source-package version for this release.2.8.2-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourceexpatVendor fix publishedDebian records a fixed source-package version for this release.2.8.2-1Debian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · esm-appslibxmltokUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · esm-appsswish-eUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · esm-appsxmlrpc-cUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivecadaverUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archiveexpatVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.2.6.1-2ubuntu0.6Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivematanzaUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivetdomUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivewbxml2Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

2 current
CVE-2026-56131 · CSAF 2.0 · revision 5 · interimSUSE Product Security TeamCVE-2026-56131
169 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • expat as component of SUSE Linux Enterprise Desktop 15 SP7
  • libexpat-devel as component of SUSE Linux Enterprise Desktop 15 SP7
  • libexpat1 as component of SUSE Linux Enterprise Desktop 15 SP7
  • libexpat1-32bit as component of SUSE Linux Enterprise Desktop 15 SP7
  • expat as component of SUSE Linux Enterprise High Performance Computing 12 SP4
  • libexpat1 as component of SUSE Linux Enterprise High Performance Computing 12 SP4
  • libexpat1-32bit as component of SUSE Linux Enterprise High Performance Computing 12 SP4
  • expat as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • libexpat-devel as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • libexpat1 as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • libexpat1-32bit as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • expat as component of SUSE Linux Enterprise High Performance Computing 15 SP1
Summary
libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).
Remediation
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
CVE-2026-56131 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitylibexpat: libexpat: Use-after-free vulnerability due to insufficient handler call depth tracking
44 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • expat as a component of Red Hat Enterprise Linux 10
  • expat-devel as a component of Red Hat Enterprise Linux 10
  • expat.src as a component of Red Hat Enterprise Linux 10
  • firefox as a component of Red Hat Enterprise Linux 10
  • firefox.src as a component of Red Hat Enterprise Linux 10
  • thunderbird as a component of Red Hat Enterprise Linux 10
  • thunderbird.src as a component of Red Hat Enterprise Linux 10
  • compat-expat1 as a component of Red Hat Enterprise Linux 6
  • compat-expat1.src as a component of Red Hat Enterprise Linux 6
  • expat as a component of Red Hat Enterprise Linux 6
  • expat-devel as a component of Red Hat Enterprise Linux 6
  • expat.src as a component of Red Hat Enterprise Linux 6
Summary
A use-after-free vulnerability in libexpat occurs because handler call depth isn't properly tracked when XML_ResumeParser is invoked during policy violations. This flaw can lead to information disclosure, data corruption, or denial of service.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-37976

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).

What

libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through local access may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through local access may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
local access → Use After Free → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-416 ↗

CWE-416: Use After Free. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.ILowIntegrity impact: A successful attack can cause a limited loss.ALowAvailability impact: A successful attack can cause a limited loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
UnauthenticatedCWE-416
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-2008expat: Mehrere Schwachstellen

Ein lokaler Angreifer kann mehrere Schwachstellen in expat ausnutzen, um einen Denial of Service Angriff durchzuführen oder potentiell Code auszuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260624Security Bulletin 24 June 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 24 June 2026, published on 24 June 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-020943libexpat projectのlibexpatにおける解放済みメモリの使用に関する脆弱性

libexpat 2.8.2 より前のバージョンでは、ポリシー違反が発生した場合にハンドラ内から XML_ResumeParser を呼び出す際、ハンドラ呼び出しの深さを追跡していませんでした。そのため、use-after-free の脆弱性が発生する可能性があります。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Action
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 19 Jun 2026 · Last source change 22 Jun 2026, 14:58 UTC · CWE-416 · Use After Free

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-37976
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    < 2.8.2 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    < 2.8.2 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
    Red Hat Product Security ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    expat as a component of Red Hat Enterprise Linux 10; expat-devel as a component of Red Hat Enterprise Linux 10; expat.src as a component of Red Hat Enterprise Linux 10; firefox as a component of Red Hat Enterprise Linux 10; firefox.src as a component of Red Hat Enterprise Linux 10; thunderbird as a component of Red Hat Enterprise Linux 10; thunderbird.src as a component of Red Hat Enterprise Linux 10; compat-expat1 as a component of Red Hat Enterprise Linux 6; compat-expat1.src as a component of Red Hat Enterprise Linux 6; expat as a component of Red Hat Enterprise Linux 6; expat-devel as a component of Red Hat Enterprise Linux 6; expat.src as a component of Red Hat Enterprise Linux 6; expat as a component of Red Hat Enterprise Linux 7; expat-devel as a component of Red Hat Enterprise Linux 7; expat-static as a component of Red Hat Enterprise Linux 7; expat.src as a component of Red Hat Enterprise Linux 7; firefox as a component of Red Hat Enterprise Linux 7; firefox.src as a component of Red Hat Enterprise Linux 7; expat as a component of Red Hat Enterprise Linux 8; expat-devel as a component of Red Hat Enterprise Linux 8; expat.src as a component of Red Hat Enterprise Linux 8; firefox as a component of Red Hat Enterprise Linux 8; firefox.src as a component of Red Hat Enterprise Linux 8; mingw-expat.src as a component of Red Hat Enterprise Linux 8; mingw32-expat as a component of Red Hat Enterprise Linux 8; mingw64-expat as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; xmlrpc-c as a component of Red Hat Enterprise Linux 8; xmlrpc-c-c++ as a component of Red Hat Enterprise Linux 8; and 13 more · Fixed: expat-main@aarch64 as a component of Red Hat Hardened Images; expat-main@src as a component of Red Hat Hardened Images; expat-main@x86_64 as a component of Red Hat Hardened Images
    After
    expat as a component of Red Hat Enterprise Linux 10; expat-devel as a component of Red Hat Enterprise Linux 10; expat.src as a component of Red Hat Enterprise Linux 10; firefox as a component of Red Hat Enterprise Linux 10; firefox.src as a component of Red Hat Enterprise Linux 10; thunderbird as a component of Red Hat Enterprise Linux 10; thunderbird.src as a component of Red Hat Enterprise Linux 10; compat-expat1 as a component of Red Hat Enterprise Linux 6; compat-expat1.src as a component of Red Hat Enterprise Linux 6; expat as a component of Red Hat Enterprise Linux 6; expat-devel as a component of Red Hat Enterprise Linux 6; expat.src as a component of Red Hat Enterprise Linux 6; expat as a component of Red Hat Enterprise Linux 7; expat-devel as a component of Red Hat Enterprise Linux 7; expat-static as a component of Red Hat Enterprise Linux 7; expat.src as a component of Red Hat Enterprise Linux 7; firefox as a component of Red Hat Enterprise Linux 7; firefox.src as a component of Red Hat Enterprise Linux 7; expat as a component of Red Hat Enterprise Linux 8; expat-devel as a component of Red Hat Enterprise Linux 8; expat.src as a component of Red Hat Enterprise Linux 8; firefox as a component of Red Hat Enterprise Linux 8; firefox.src as a component of Red Hat Enterprise Linux 8; mingw-expat.src as a component of Red Hat Enterprise Linux 8; mingw32-expat as a component of Red Hat Enterprise Linux 8; mingw64-expat as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; xmlrpc-c as a component of Red Hat Enterprise Linux 8; xmlrpc-c-c++ as a component of Red Hat Enterprise Linux 8; and 14 more · Fixed: expat-main@aarch64 as a component of Red Hat Hardened Images; expat-main@src as a component of Red Hat Hardened Images; expat-main@x86_64 as a component of Red Hat Hardened Images
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-37976↗Vendor CSAF · SUSE Product Security Team↗Red Hat Product Security security advisory↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-56131 · cve.blacktree.nl