CVE-2026-93990

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-20. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — Patch released this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequences to be accepted. Attackers can supply UTF-16 encoded XML containing lone high surrogates that consume the following code unit, causing Expat to pass unpaired surrogates to applications built with XML_UNICODE and to silently replace input characters in other builds.

CVSS v3
7.5
EG Score
7.5HIGHhigh confidence
EG Risk
49
EG Risk 49/100CISA SSVC

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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
32nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 19, 2026

Last Modified

September 28, 2026

Advisory Details (3)

Auto-updated Sep 19, 2026
Patch available. Sources: github_pr, github_commit.
generic

GitHub - libexpat/libexpat: :herb: Fast streaming XML parser written in C99 with >90% test coverage; moved from SourceForge to GitHub · GitHub

https://github.com/libexpat/libexpat
github_commit

commit ff6e1d7e750b (libexpat/libexpat)

Fix landed in libexpat/libexpat commit ff6e1d7e750b — awaiting tagged release

https://github.com/libexpat/libexpat/commit/ff6e1d7e750bbe245178f51a47a965dc8342861a
github_pr

[CVE-REQUESTED] lib: Reject UTF-16 high surrogate not followed by a low surrogate

Fix merged in libexpat/libexpat PR #1282 on 2026-09-18 — awaiting tagged release

https://github.com/libexpat/libexpat/pull/1282

Vendor Advisories for CVE-2026-93990(5)

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

Patch Availability(4)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatexpat-0:2.7.3-1.el10_2.52026-09-30redhat
redhatexpat-0:2.5.0-6.el9_8.52026-09-29redhat
redhatexpat-0:2.5.0-4.el8_102026-09-28redhat
redhatexpat-main-2.8.4-0.2.hum12026-09-24redhat

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

(6 across 6 ecosystems)
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
expat—
  • every version up to 2.8.5-r0: fixed in 2.8.5-r0
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
expat—
  • every version up to 2.8.5-r0: fixed in 2.8.5-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
expat—
  • every version up to 2.8.5-r0: fixed in 2.8.5-r0
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
expat2.5.0-1, 2.5.0-1+deb12u1, 2.5.0-1+deb12u2, 2.5.0-1+deb12u3
  • every version up to 2.5.0-1+deb12u4: fixed in 2.5.0-1+deb12u4
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
expat2.7.1-2 ... 2.8.5-2 (17 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
expat2.7.1-2 ... 2.8.4-1 (14 versions)
  • every version up to 2.8.4-2: fixed in 2.8.4-2
—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 44× in last 7d / 95× 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. 2026-10-05 03:14 UTCEG score recompute
  2. 2026-10-05 03:14 UTCVendor advisory
  3. 2026-10-05 03:14 UTCGHSA enrichment
  4. 2026-10-04 23:23 UTCEPSS rescore
  5. 2026-10-04 14:28 UTCVendor advisory
  6. 2026-10-04 14:28 UTCGHSA enrichment
  7. 2026-10-04 01:41 UTCEG score recompute
  8. 2026-10-04 01:41 UTCVendor advisory
  9. 2026-10-04 01:41 UTCGHSA enrichment
  10. 2026-10-03 14:26 UTCEPSS rescore
  11. 2026-10-03 12:49 UTCVendor advisory
  12. 2026-10-03 12:49 UTCGHSA enrichment
  13. 2026-10-03 00:02 UTCEG score recompute
  14. 2026-10-03 00:02 UTCVendor advisory
  15. 2026-10-03 00:02 UTCGHSA enrichment
  16. 2026-10-02 17:57 UTCEPSS rescore
  17. 2026-10-02 11:15 UTCVendor advisory
  18. 2026-10-02 11:15 UTCGHSA enrichment
  19. 2026-10-01 22:27 UTCEG score recompute
  20. 2026-10-01 22:27 UTCVendor advisory
  21. 2026-10-01 22:27 UTCGHSA enrichment
  22. 2026-10-01 19:51 UTCEPSS rescore
  23. 2026-10-01 09:38 UTCVendor advisory
  24. 2026-10-01 09:38 UTCGHSA enrichment
  25. 2026-09-30 20:52 UTCEG score recompute
Show 70 more
  1. 2026-09-30 20:52 UTCVendor advisory
  2. 2026-09-30 20:52 UTCGHSA enrichment
  3. 2026-09-30 15:04 UTCEPSS rescore
  4. 2026-09-30 08:06 UTCVendor advisory
  5. 2026-09-30 08:06 UTCGHSA enrichment
  6. 2026-09-29 19:20 UTCEG score recompute
  7. 2026-09-29 19:20 UTCVendor advisory
  8. 2026-09-29 19:20 UTCGHSA enrichment
  9. 2026-09-29 06:31 UTCEG score recompute
  10. 2026-09-29 06:31 UTCVendor advisory
  11. 2026-09-29 06:31 UTCGHSA enrichment
  12. 2026-09-28 17:45 UTCEG score recompute
  13. 2026-09-28 17:45 UTCVendor advisory
  14. 2026-09-28 17:45 UTCGHSA enrichment
  15. 2026-09-28 16:35 UTCEG score recompute
  16. 2026-09-28 16:35 UTCVendor advisory
  17. 2026-09-28 16:35 UTCGHSA enrichment
  18. 2026-09-28 13:52 UTCEPSS rescore
  19. 2026-09-28 13:52 UTCEPSS rescore
  20. 2026-09-28 04:56 UTCVendor advisory
  21. 2026-09-28 04:56 UTCGHSA enrichment
  22. 2026-09-27 16:09 UTCEG score recompute
  23. 2026-09-27 16:09 UTCVendor advisory
  24. 2026-09-27 16:09 UTCGHSA enrichment
  25. 2026-09-27 13:49 UTCEPSS rescore
  26. 2026-09-27 03:23 UTCEG score recompute
  27. 2026-09-27 03:23 UTCVendor advisory
  28. 2026-09-27 03:23 UTCGHSA enrichment
  29. 2026-09-26 15:59 UTCEPSS rescore
  30. 2026-09-26 14:37 UTCVendor advisory
  31. 2026-09-26 14:37 UTCGHSA enrichment
  32. 2026-09-26 01:32 UTCEG score recompute
  33. 2026-09-26 01:32 UTCVendor advisory
  34. 2026-09-26 01:32 UTCGHSA enrichment
  35. 2026-09-25 12:43 UTCVendor advisory
  36. 2026-09-25 12:43 UTCGHSA enrichment
  37. 2026-09-24 23:57 UTCEG score recompute
  38. 2026-09-24 23:57 UTCVendor advisory
  39. 2026-09-24 23:57 UTCGHSA enrichment
  40. 2026-09-24 14:04 UTCEPSS rescore
  41. 2026-09-24 10:52 UTCVendor advisory
  42. 2026-09-24 10:52 UTCGHSA enrichment
  43. 2026-09-23 22:05 UTCEG score recompute
  44. 2026-09-23 22:05 UTCVendor advisory
  45. 2026-09-23 22:05 UTCGHSA enrichment
  46. 2026-09-23 17:54 UTCEPSS rescore
  47. 2026-09-23 09:19 UTCVendor advisory
  48. 2026-09-23 09:19 UTCGHSA enrichment
  49. 2026-09-22 20:32 UTCVendor advisory
  50. 2026-09-22 20:32 UTCGHSA enrichment
  51. 2026-09-22 17:00 UTCEG score recompute
  52. 2026-09-22 17:00 UTCVendor advisory
  53. 2026-09-22 16:59 UTCGHSA enrichment
  54. 2026-09-22 16:01 UTCEPSS rescore
  55. 2026-09-22 04:09 UTCEG score recompute
  56. 2026-09-22 04:09 UTCGHSA enrichment
  57. 2026-09-21 21:09 UTCEPSS rescore
  58. 2026-09-21 15:23 UTCEG score recompute
  59. 2026-09-21 15:23 UTCGHSA enrichment
  60. 2026-09-21 15:15 UTCEG score recompute
  61. 2026-09-21 15:15 UTCGHSA enrichment
  62. 2026-09-21 13:47 UTCGHSA enrichment
  63. 2026-09-21 01:01 UTCEG score recompute
  64. 2026-09-21 01:01 UTCGHSA enrichment
  65. 2026-09-20 20:16 UTCEPSS rescore
  66. 2026-09-20 12:15 UTCEG score recompute
  67. 2026-09-20 12:14 UTCGHSA enrichment
  68. 2026-09-19 23:27 UTCEG score recompute
  69. 2026-09-19 23:00 UTCEG score recompute
  70. 2026-09-19 23:00 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same vendor + same CWE)

Same vendor

1 shown

redhat:RHSA-2026:72448

Frequently asked(5)

What is CVE-2026-93990?
CVE-2026-93990 is a high vulnerability published on September 19, 2026. Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequences to be accepted. Attackers can supply UTF-16 encoded XML containing lone high surrogates that consume the following code unit, causing Expat to pass unpaired…
When was CVE-2026-93990 disclosed?
CVE-2026-93990 was first published on September 19, 2026, with the most recent update on September 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-93990 actively exploited?
CVE-2026-93990 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (32nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-93990?
CVE-2026-93990 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-93990?
A fix for CVE-2026-93990 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-93990 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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