CVE-2026-66046

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-08-18. a secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated 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: 1%CVSS: 7.5Exploit: None knownExposed: 0

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

Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
47%
KEV
Not listed

Published

August 18, 2026

Last Modified

September 18, 2026

Advisory Details (2)

Auto-updated Aug 18, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr.
generic

Expat Denial of Service via storeAtts() Quadratic Complexity | Advisories | VulnCheck

https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity
github_pr

[CVE-2026-66046] lib: Migrate `.isCdata` lookup from a linear loop to a hash table lookup

Fix merged in libexpat/libexpat PR #1321 on 2026-08-18 — awaiting tagged release

https://github.com/libexpat/libexpat/pull/1321

Vendor Advisories for CVE-2026-66046(1)

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

Affected Packages

(7 across 7 ecosystems)
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.4-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.4-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.4-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
expat—2.8.4-r0—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
expat2.5.0-1 ... 2.8.4-1 (29 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
expat2.7.1-2 ... 2.8.4-1 (14 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
expat2.7.1-2 ... 2.8.3-1~deb13u1 (13 versions)2.8.4-1—

Weakness Classification(1)

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

All Vendor Advisories

(1)

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 41× in last 7d / 135× 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 144 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-66046?
CVE-2026-66046 is a high vulnerability published on August 18, 2026. Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA…
When was CVE-2026-66046 disclosed?
CVE-2026-66046 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66046 actively exploited?
CVE-2026-66046 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 53.3% of all scored CVEs.
What is the CVSS score of CVE-2026-66046?
CVE-2026-66046 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-66046?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66046, 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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