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
Trending — 4 sources updated this week
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
3%
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.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 15× in last 7d / 82× 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.

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

Related CVEs(same vendor + same CWE)

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 96.7% 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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