LiveActive security incident?Get immediate response
CVE Record

CVE-2026-4177: YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter

YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter. The heap overflow occurs when class names exceed the initial 512-byte allocation. The base64 decoder could read past the buffer end on trailing newlines. strtok mutated n->type_id in place, corrupting shared node data. A memory leak occurred in syck_hdlr_add_anchor when a node already had an anchor. The incoming anchor string 'a' was leaked on early return.

CriticalCVSS 9.1Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-4177 affects Perl YAML::Syck through 1.36. A memory safety flaw in YAML emitting can overflow heap memory when long class names are processed, with additional parser-related memory issues. The published CVSS is 9.1, but the provided sources do not show active exploitation.

Executive priority

Treat as urgent for systems that process external YAML or include YAML::Syck in exposed services. Prioritize inventory and patching because the issue is critical severity and memory unsafe, even though active exploitation is not evidenced in the provided sources.

Technical view

The source bundle describes a heap buffer overflow in the YAML emitter, an out-of-bounds read in base64 decoding with trailing newlines, in-place mutation of n->type_id via strtok, and an anchor-related memory leak. The CVSS vector indicates network attack, low complexity, no privileges, no user interaction, high confidentiality impact, and high availability impact.

Likely exposure

Exposure is most likely in Perl applications, services, or packaged products using YAML::Syck or YAML-Syck versions through 1.36, especially where untrusted YAML, object tags, or serialized class names can reach parsing or emitting paths.

Exploitation context

The CVE is not listed as KEV in the provided bundle. No cited source states active exploitation. The CVSS vector suggests remote unauthenticated reachability may be possible in vulnerable deployments, but real exposure depends on how YAML::Syck is used.

Researcher notes

The affected-version data in the source bundle is internally uneven: narrative text says versions through 1.36, while the structured affected entry lists version 0 with defaultStatus unaffected. Prefer vendor release notes, patch references, and distribution advisories for final applicability decisions.

Mitigation direction

  • Inventory Perl dependencies for YAML::Syck or YAML-Syck.
  • Upgrade from versions through 1.36 to a fixed vendor-supported release.
  • Apply relevant Red Hat advisories where using Red Hat packages.
  • Restrict untrusted YAML input until patched, where operationally feasible.
  • Check vendor guidance if pinned or bundled dependencies cannot be upgraded.

Validation and detection

  • Check dependency manifests and runtime package inventories for YAML-Syck versions through 1.36.
  • Confirm deployed systems run a fixed release or vendor-patched package.
  • Map application paths that parse or emit attacker-controlled YAML.
  • Review SBOMs and container images for bundled vulnerable Perl modules.
  • Track Red Hat CSAF, errata, and CVE pages for status changes.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-120: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-122: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-4177 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
3ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.1CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H3.95.2CISA-ADP
7.3CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L3.93.4redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9.1Critical
CVSS 3.1 vector shape for CVE-2026-4177Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPperl-YAML-Syck: YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter
other:Red Hat severity ratingcvssV3_1
  • 2026-03-16T23:01:43.396Z: Reported to Red Hat.
  • 2026-03-16T22:30:25.367Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
TODDRYAML::SyckYAML-Syck, 0unaffected
Weakness

CWE details

CWE-120CWE-122

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.