CVE-2026-4177

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-03-17. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: None knownExposed: 0

A fix is available — apply it.

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.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
56(Track)
EG Risk 56/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
37%
KEV
Not listed

Published

March 17, 2026

Last Modified

July 15, 2026

Advisory Details (8)

Auto-updated Sep 16, 2026
Patch available. Sources: redhat.
redhat Patch Available

Affected: Red Hat Enterprise Linux 6",

https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4177.json
redhat Patch Available

2448277 – (CVE-2026-4177) CVE-2026-4177 perl-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

Affected: Red Hat Enterprise Linux 8

https://bugzilla.redhat.com/show_bug.cgi?id=2448277
redhat Patch Available

CVE-2026-4177 - Red Hat Customer Portal

Affected: Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to a

https://access.redhat.com/security/cve/CVE-2026-4177
redhat Patch Available

Affected: Red Hat Enterprise Linux 7 Extended Lifecycle Support.

https://access.redhat.com/errata/RHSA-2026:8311
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2026:6470
generic

oss-security - 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

http://www.openwall.com/lists/oss-security/2026/03/16/6
generic

Changes - metacpan.org

https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21
generic
https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch

Vendor Advisories for CVE-2026-4177(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatperl-YAML-Syck-0:1.27-3.el7_9.12026-04-15redhat
redhatperl-YAML-Syck-0:1.30-6.el8_102026-04-02redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(5 across 5 ecosystems)
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
perl-yaml-syck—1.45-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
libyaml-syck-perl1.34-11.34-1+deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
libyaml-syck-perl1.34-2, 1.34-2+deb12u11.34-2+deb12u2—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libyaml-syck-perl1.34-2, 1.34-2+deb13u11.34-2+deb13u2—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libyaml-syck-perl1.34-2, 1.34-3, 1.34-4, 1.36-11.36-2—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 4× in last 7d / 22× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 156 total refreshes for this CVE.

  1. 2026-09-20 20:16 UTCEPSS rescore
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-16 14:08 UTCEPSS rescore
  4. 2026-09-16 05:15 UTCEPSS rescore
  5. 2026-09-13 16:47 UTCEPSS rescore
  6. 2026-09-11 14:53 UTCEPSS rescore
  7. 2026-09-10 09:35 UTCEPSS rescore
  8. 2026-09-08 22:01 UTCEPSS rescore
  9. 2026-09-07 16:01 UTCEPSS rescore
  10. 2026-09-06 13:47 UTCEPSS rescore
  11. 2026-09-04 05:06 UTCEPSS rescore
  12. 2026-09-02 18:08 UTCOSV refresh
  13. 2026-09-02 14:12 UTCEPSS rescore
  14. 2026-09-01 13:54 UTCEPSS rescore
  15. 2026-09-01 04:40 UTCEPSS rescore
  16. 2026-08-30 19:17 UTCEPSS rescore
  17. 2026-08-30 01:22 UTCEPSS rescore
  18. 2026-08-28 21:41 UTCEPSS rescore
  19. 2026-08-27 14:25 UTCEPSS rescore
  20. 2026-08-26 14:46 UTCEPSS rescore
  21. 2026-08-25 13:49 UTCEPSS rescore
  22. 2026-08-23 00:19 UTCEPSS rescore
  23. 2026-08-21 23:49 UTCEPSS rescore
  24. 2026-08-20 22:55 UTCEPSS rescore
  25. 2026-08-19 17:04 UTCEPSS rescore
Show 75 more
  1. 2026-08-18 13:48 UTCEPSS rescore
  2. 2026-08-17 13:47 UTCEPSS rescore
  3. 2026-08-16 14:56 UTCEPSS rescore
  4. 2026-08-16 11:22 UTCEG score recompute
  5. 2026-08-16 11:22 UTCVendor advisory
  6. 2026-08-16 11:22 UTCGHSA enrichment
  7. 2026-08-16 02:14 UTCEPSS rescore
  8. 2026-08-15 01:30 UTCEPSS rescore
  9. 2026-08-15 00:19 UTCVendor advisory
  10. 2026-08-15 00:19 UTCGHSA enrichment
  11. 2026-08-14 20:06 UTCVendor advisory
  12. 2026-08-14 20:06 UTCGHSA enrichment
  13. 2026-08-14 15:54 UTCVendor advisory
  14. 2026-08-14 15:54 UTCGHSA enrichment
  15. 2026-08-14 11:41 UTCVendor advisory
  16. 2026-08-14 11:41 UTCGHSA enrichment
  17. 2026-08-14 07:29 UTCEG score recompute
  18. 2026-08-14 07:29 UTCVendor advisory
  19. 2026-08-14 07:29 UTCGHSA enrichment
  20. 2026-08-13 22:00 UTCEPSS rescore
  21. 2026-08-13 02:28 UTCVendor advisory
  22. 2026-08-13 02:28 UTCGHSA enrichment
  23. 2026-08-12 22:16 UTCEG score recompute
  24. 2026-08-12 22:16 UTCVendor advisory
  25. 2026-08-12 22:16 UTCGHSA enrichment
  26. 2026-08-12 13:51 UTCEPSS rescore
  27. 2026-08-12 01:47 UTCVendor advisory
  28. 2026-08-12 01:47 UTCGHSA enrichment
  29. 2026-08-11 21:34 UTCEG score recompute
  30. 2026-08-11 21:34 UTCVendor advisory
  31. 2026-08-11 21:34 UTCGHSA enrichment
  32. 2026-08-11 08:54 UTCVendor advisory
  33. 2026-08-11 08:54 UTCGHSA enrichment
  34. 2026-08-11 04:41 UTCEG score recompute
  35. 2026-08-11 04:41 UTCVendor advisory
  36. 2026-08-11 04:41 UTCGHSA enrichment
  37. 2026-08-11 00:00 UTCEPSS rescore
  38. 2026-08-10 12:15 UTCVendor advisory
  39. 2026-08-10 12:15 UTCGHSA enrichment
  40. 2026-08-10 06:30 UTCVendor advisory
  41. 2026-08-10 06:30 UTCGHSA enrichment
  42. 2026-08-10 02:04 UTCVendor advisory
  43. 2026-08-10 02:04 UTCGHSA enrichment
  44. 2026-08-09 21:48 UTCVendor advisory
  45. 2026-08-09 21:48 UTCGHSA enrichment
  46. 2026-08-09 17:36 UTCEG score recompute
  47. 2026-08-09 17:36 UTCVendor advisory
  48. 2026-08-09 17:36 UTCGHSA enrichment
  49. 2026-08-09 13:46 UTCEPSS rescore
  50. 2026-08-09 13:24 UTCVendor advisory
  51. 2026-08-09 13:24 UTCGHSA enrichment
  52. 2026-08-09 07:04 UTCEG score recompute
  53. 2026-08-09 07:04 UTCVendor advisory
  54. 2026-08-09 07:04 UTCGHSA enrichment
  55. 2026-08-08 16:37 UTCEPSS rescore
  56. 2026-08-08 10:33 UTCVendor advisory
  57. 2026-08-08 10:33 UTCGHSA enrichment
  58. 2026-08-08 06:20 UTCVendor advisory
  59. 2026-08-08 06:20 UTCGHSA enrichment
  60. 2026-08-08 02:07 UTCVendor advisory
  61. 2026-08-08 02:07 UTCGHSA enrichment
  62. 2026-08-07 21:55 UTCVendor advisory
  63. 2026-08-07 21:55 UTCGHSA enrichment
  64. 2026-08-07 17:42 UTCEG score recompute
  65. 2026-08-07 17:42 UTCVendor advisory
  66. 2026-08-07 17:42 UTCGHSA enrichment
  67. 2026-08-06 19:33 UTCEG score recompute
  68. 2026-08-06 19:33 UTCVendor advisory
  69. 2026-08-06 19:33 UTCGHSA enrichment
  70. 2026-08-06 13:47 UTCEPSS rescore
  71. 2026-08-06 10:29 UTCVendor advisory
  72. 2026-08-06 10:29 UTCGHSA enrichment
  73. 2026-08-06 05:56 UTCVendor advisory
  74. 2026-08-06 05:56 UTCGHSA enrichment
  75. 2026-08-06 01:43 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-4177?
CVE-2026-4177 is a critical vulnerability published on March 17, 2026. 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…
When was CVE-2026-4177 disclosed?
CVE-2026-4177 was first published in the National Vulnerability Database on March 17, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-4177 actively exploited?
CVE-2026-4177 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 63.3% of all scored CVEs.
What is the CVSS score of CVE-2026-4177?
CVE-2026-4177 has a CVSS v3.1 base score of 9.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-4177?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-4177, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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