CVE-2026-56406

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

Score 6.9 from GitHub Security Advisory published 2026-06-21. a secondary CVSS source baseline 6.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in XML_Parse.

CVSS v3
6.9
EG Score
6.9(medium)
EG Risk
36(Track)
EG Risk 36/100SSVC: 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
Severity69% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
4%
KEV
Not listed

Published

June 21, 2026

Last Modified

June 23, 2026

Advisory Details (1)

Auto-updated Jun 22, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr.
github_pr

[CVE-2026-56406] lib: Copy overflow check from `XML_Parse` to `XML_ParseBuffer`

Fix merged in libexpat/libexpat PR #1255 on 2026-05-31 — awaiting tagged release

https://github.com/libexpat/libexpat/pull/1255

Vendor Advisories for CVE-2026-56406(2)

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

Affected Packages

(8 across 8 ecosystems)
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.2-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.2-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.2-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.2-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
expat2.2.10-2 ... 2.8.2-1~deb13u1 (47 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
expat2.5.0-1, 2.5.0-1+deb12u1, 2.5.0-1+deb12u22.5.0-1+deb12u3—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
expat2.7.1-2 ... 2.8.1-1 (9 versions)2.8.2-1~deb13u1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
expat2.7.1-2 ... 2.8.2-1~deb13u1 (10 versions)2.8.2-1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 60× 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 210 total refreshes for this CVE.

  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-10 09:35 UTCEPSS rescore
  3. 2026-09-08 22:01 UTCEPSS rescore
  4. 2026-09-07 16:01 UTCEPSS rescore
  5. 2026-09-06 13:47 UTCEPSS rescore
  6. 2026-09-04 05:07 UTCEPSS rescore
  7. 2026-09-02 14:12 UTCEPSS rescore
  8. 2026-09-01 13:54 UTCEPSS rescore
  9. 2026-09-01 04:40 UTCEPSS rescore
  10. 2026-08-30 20:41 UTCEG score recompute
  11. 2026-08-30 20:41 UTCVendor advisory
  12. 2026-08-30 20:41 UTCGHSA enrichment
  13. 2026-08-30 19:17 UTCEPSS rescore
  14. 2026-08-30 01:22 UTCEPSS rescore
  15. 2026-08-28 21:42 UTCEPSS rescore
  16. 2026-08-27 14:25 UTCEPSS rescore
  17. 2026-08-26 14:46 UTCEPSS rescore
  18. 2026-08-25 13:49 UTCEPSS rescore
  19. 2026-08-24 22:15 UTCEG score recompute
  20. 2026-08-24 22:15 UTCVendor advisory
  21. 2026-08-24 22:15 UTCGHSA enrichment
  22. 2026-08-23 21:25 UTCEG score recompute
  23. 2026-08-23 21:25 UTCVendor advisory
  24. 2026-08-23 21:25 UTCGHSA enrichment
  25. 2026-08-23 00:19 UTCEPSS rescore
Show 75 more
  1. 2026-08-22 22:54 UTCEG score recompute
  2. 2026-08-22 22:54 UTCVendor advisory
  3. 2026-08-22 22:54 UTCGHSA enrichment
  4. 2026-08-21 23:49 UTCEPSS rescore
  5. 2026-08-21 06:22 UTCEG score recompute
  6. 2026-08-21 06:22 UTCVendor advisory
  7. 2026-08-21 06:22 UTCGHSA enrichment
  8. 2026-08-20 22:55 UTCEPSS rescore
  9. 2026-08-20 07:53 UTCEG score recompute
  10. 2026-08-20 07:53 UTCVendor advisory
  11. 2026-08-20 07:53 UTCGHSA enrichment
  12. 2026-08-19 17:04 UTCEPSS rescore
  13. 2026-08-19 05:47 UTCEG score recompute
  14. 2026-08-19 05:47 UTCVendor advisory
  15. 2026-08-19 05:47 UTCGHSA enrichment
  16. 2026-08-18 13:48 UTCEPSS rescore
  17. 2026-08-17 13:47 UTCEPSS rescore
  18. 2026-08-16 23:46 UTCEG score recompute
  19. 2026-08-16 23:46 UTCVendor advisory
  20. 2026-08-16 23:46 UTCGHSA enrichment
  21. 2026-08-16 14:56 UTCEPSS rescore
  22. 2026-08-16 02:14 UTCEPSS rescore
  23. 2026-08-16 01:16 UTCVendor advisory
  24. 2026-08-16 01:16 UTCGHSA enrichment
  25. 2026-08-15 02:46 UTCEG score recompute
  26. 2026-08-15 02:46 UTCVendor advisory
  27. 2026-08-15 02:46 UTCGHSA enrichment
  28. 2026-08-15 01:30 UTCEPSS rescore
  29. 2026-08-14 04:12 UTCEG score recompute
  30. 2026-08-14 04:12 UTCVendor advisory
  31. 2026-08-14 04:12 UTCGHSA enrichment
  32. 2026-08-13 22:00 UTCEPSS rescore
  33. 2026-08-13 05:42 UTCEG score recompute
  34. 2026-08-13 05:42 UTCVendor advisory
  35. 2026-08-13 05:42 UTCGHSA enrichment
  36. 2026-08-12 13:51 UTCEPSS rescore
  37. 2026-08-12 07:13 UTCVendor advisory
  38. 2026-08-12 07:13 UTCGHSA enrichment
  39. 2026-08-11 08:42 UTCEG score recompute
  40. 2026-08-11 08:42 UTCVendor advisory
  41. 2026-08-11 08:42 UTCGHSA enrichment
  42. 2026-08-11 00:00 UTCEPSS rescore
  43. 2026-08-10 10:13 UTCEG score recompute
  44. 2026-08-10 10:13 UTCVendor advisory
  45. 2026-08-10 10:13 UTCGHSA enrichment
  46. 2026-08-09 13:46 UTCEPSS rescore
  47. 2026-08-09 11:43 UTCEG score recompute
  48. 2026-08-09 11:43 UTCVendor advisory
  49. 2026-08-09 11:43 UTCGHSA enrichment
  50. 2026-08-08 16:37 UTCEPSS rescore
  51. 2026-08-08 13:10 UTCEG score recompute
  52. 2026-08-08 13:10 UTCVendor advisory
  53. 2026-08-08 13:10 UTCGHSA enrichment
  54. 2026-08-07 14:40 UTCGHSA enrichment
  55. 2026-08-06 16:11 UTCEG score recompute
  56. 2026-08-06 16:11 UTCVendor advisory
  57. 2026-08-06 16:11 UTCGHSA enrichment
  58. 2026-08-06 13:47 UTCEPSS rescore
  59. 2026-08-05 19:17 UTCEPSS rescore
  60. 2026-08-05 17:40 UTCGHSA enrichment
  61. 2026-08-04 18:30 UTCEG score recompute
  62. 2026-08-04 18:30 UTCVendor advisory
  63. 2026-08-04 18:30 UTCGHSA enrichment
  64. 2026-08-04 15:10 UTCEPSS rescore
  65. 2026-08-04 10:39 UTCEPSS rescore
  66. 2026-08-03 19:32 UTCEG score recompute
  67. 2026-08-03 19:32 UTCVendor advisory
  68. 2026-08-03 19:32 UTCGHSA enrichment
  69. 2026-08-03 10:36 UTCEPSS rescore
  70. 2026-08-02 21:03 UTCEG score recompute
  71. 2026-08-02 21:03 UTCVendor advisory
  72. 2026-08-02 21:03 UTCGHSA enrichment
  73. 2026-08-02 02:27 UTCEPSS rescore
  74. 2026-08-01 22:33 UTCEG score recompute
  75. 2026-08-01 22:33 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-56406?
CVE-2026-56406 is a medium vulnerability published on June 21, 2026. libexpat before 2.8.2 has an integer overflow in XMLParseBuffer because it lacked a check that was present in XMLParse.
When was CVE-2026-56406 disclosed?
CVE-2026-56406 was first published in the National Vulnerability Database on June 21, 2026, with the most recent update on June 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56406 actively exploited?
CVE-2026-56406 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 96.4% of all scored CVEs.
What is the CVSS score of CVE-2026-56406?
CVE-2026-56406 has a CVSS v3 base score of 6.9 (NVD).
How do I remediate CVE-2026-56406?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56406, 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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