Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.13% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-13713High confidence
YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack
TODDR · YAML::Syck
6.2MediumCVSS 3.1
Scheduled
Patch availableMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, unchanged from published severity.unchanged
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
- Confirm that the asset runs TODDR YAML::Syck and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Distribution package intelligence
5 package statesRelease-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
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 release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | libyaml-syck-perl | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.34-2+deb13u3 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian bookwormbookworm · source | libyaml-syck-perl | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.34-2+deb12u3 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian forkyforky · source | libyaml-syck-perl | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.47-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian sidsid · source | libyaml-syck-perl | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.47-1 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Ubuntu 24.04 LTSnoble · esm-apps | libyaml-syck-perl | Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 5 Oct 2026 |
Direct vendor intelligence
1 currentAuthoritative 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.
CVE-2026-13713 · CSAF 2.0 · revision 3 · finalRed Hat Product SecurityYAML-Syck: YAML::Syck: Denial of Service via crafted YAML document
The vendor explicitly identifies these products as affected by this CVE.
- perl-YAML-Syck.src as a component of Red Hat Enterprise Linux 6
- perl-YAML-Syck as a component of Red Hat Enterprise Linux 7
- perl-YAML-Syck.src as a component of Red Hat Enterprise Linux 7
- Summary
- A flaw was found in YAML::Syck. This vulnerability allows a remote attacker to cause a denial of service (DoS) by providing a specially crafted YAML document. The flaw occurs due to a use-after-free and double-free condition when an anchor node is redefined while still on the parser's value stack, leading to the interpreter crashing.
- Remediation
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available01
What, why and how
YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.
What
YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.
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 disrupt the affected service.
What
YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.
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 disrupt the affected service.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.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 None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.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 → disrupt the affected service
- Attack surface
- Local
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- 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:L/PR:N/UI:N/S:U/C:N/I:N/A:HCommon 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.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.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.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major 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.
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
- perl-YAML-Syck-0:1.30-7.el8_10.aarch64 as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-0:1.30-7.el8_10.ppc64le as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-0:1.30-7.el8_10.s390x as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-0:1.30-7.el8_10.src as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-0:1.30-7.el8_10.x86_64 as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debuginfo-0:1.30-7.el8_10.aarch64 as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debuginfo-0:1.30-7.el8_10.ppc64le as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debuginfo-0:1.30-7.el8_10.s390x as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debuginfo-0:1.30-7.el8_10.x86_64 as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debugsource-0:1.30-7.el8_10.aarch64 as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debugsource-0:1.30-7.el8_10.ppc64le as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debugsource-0:1.30-7.el8_10.s390x as a component of Red Hat Enterprise Linux CRB (v. 8)
- perl-YAML-Syck-debugsource-0:1.30-7.el8_10.x86_64 as a component of Red Hat Enterprise Linux CRB (v. 8)
- Action
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
- Workaround
- No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 16 Jul 2026 · Last source change 17 Jul 2026, 13:18 UTC · CWE-416 · Use After Free
CVE recordCVE.org · 5.2
CVSS sourceCISA ADP
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-45052
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD not scheduled
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- < 1.47 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- < 1.47 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
- Remediation statusRemediation status changed from Awaiting fix to Patch available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Patch available
CVE published
Fixed release recorded from official guidance
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.