CVE-2026-93990

HIGHPre-NVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

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, GitHub Security Advisory, a secondary CVSS source

Also known asEUVD-2026-83618 (ENISA EUVD) · GHSA-rfp9-ffqc-h4x8 (GitHub Security Advisories)Source: ENISA EUVD

7.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • 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
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
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
36th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track 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). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

September 19, 2026

Last Modified

November 10, 2026

Advisory Details (3)

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

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 pull request

[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

Patch Availability(7)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatopenshift/ose-rhel-coreos-9:4.22.9.8.202610241758-02026-10-27redhat
redhatrhui5/rhua-rhel9:17919786932026-10-14redhat
redhatcostmanagement/costmanagement-ui-rhel10:17914608512026-10-08redhat
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

(7 across 7 ecosystems)
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
expat—
  • every version up to 2.8.5-r0: fixed in 2.8.5-r0
—
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 up to 2.9.0-1~deb13u1: fixed in 2.9.0-1~deb13u1
—
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.

Data Freshness Timeline

(refreshed 15× in last 7d / 44× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 198 rows on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 98 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 16:58 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  2. 2026-11-12 16:35 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  3. 2026-11-11 16:41 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  4. 2026-11-11 04:01 UTCEchelonGraph re-scored
  5. 2026-11-11 04:01 UTCVendor advisory
  6. 2026-11-11 04:01 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  7. 2026-11-10 16:46 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  8. 2026-11-10 13:28 UTCEchelonGraph re-scored
  9. 2026-11-10 13:28 UTCVendor advisory
  10. 2026-11-10 13:28 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  11. 2026-11-10 13:01 UTCEchelonGraph re-scored
  12. 2026-11-10 13:01 UTCVendor advisory
  13. 2026-11-10 13:01 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  14. 2026-11-09 16:36 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  15. 2026-11-08 16:41 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  16. 2026-11-08 14:16 UTCEchelonGraph re-scored
  17. 2026-11-08 14:16 UTCVendor advisory
  18. 2026-11-08 14:16 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  19. 2026-11-07 16:40 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  20. 2026-11-06 16:40 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  21. 2026-11-05 16:39 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  22. 2026-11-04 16:37 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  23. 2026-11-03 18:47 UTCEchelonGraph re-scored
  24. 2026-11-03 18:47 UTCVendor advisory
  25. 2026-11-03 18:47 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
Show 75 more
  1. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  2. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  3. 2026-11-01 16:36 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  4. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  5. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  6. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  7. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  8. 2026-10-27 18:57 UTCEchelonGraph re-scored
  9. 2026-10-27 18:57 UTCVendor advisory
  10. 2026-10-27 18:57 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  11. 2026-10-27 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  12. 2026-10-26 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  13. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  14. 2026-10-25 13:49 UTCEchelonGraph re-scored
  15. 2026-10-24 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  16. 2026-10-23 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  17. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  18. 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  19. 2026-10-20 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  20. 2026-10-20 00:32 UTCEchelonGraph re-scored
  21. 2026-10-20 00:32 UTCVendor advisory
  22. 2026-10-20 00:32 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  23. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  24. 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  25. 2026-10-18 02:58 UTCEchelonGraph re-scored
  26. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  27. 2026-10-16 16:45 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  28. 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  29. 2026-10-14 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  30. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  31. 2026-10-13 04:22 UTCEchelonGraph re-scored
  32. 2026-10-13 04:22 UTCVendor advisory
  33. 2026-10-13 04:21 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  34. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  35. 2026-10-12 14:42 UTCEchelonGraph re-scored
  36. 2026-10-12 02:45 UTCVendor advisory
  37. 2026-10-12 02:45 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  38. 2026-10-11 19:12 UTCEchelonGraph re-scored
  39. 2026-10-11 16:28 UTCEchelonGraph re-scored
  40. 2026-10-11 13:56 UTCEchelonGraph re-scored
  41. 2026-10-11 13:56 UTCVendor advisory
  42. 2026-10-11 13:56 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  43. 2026-10-11 13:50 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  44. 2026-10-11 13:41 UTCEchelonGraph re-scored
  45. 2026-10-11 00:01 UTCEchelonGraph re-scored
  46. 2026-10-11 00:01 UTCVendor advisory
  47. 2026-10-11 00:00 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  48. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  49. 2026-10-10 11:12 UTCVendor advisory
  50. 2026-10-10 11:12 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  51. 2026-10-09 22:26 UTCEchelonGraph re-scored
  52. 2026-10-09 22:26 UTCVendor advisory
  53. 2026-10-09 22:26 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  54. 2026-10-09 20:08 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  55. 2026-10-09 09:39 UTCVendor advisory
  56. 2026-10-09 09:39 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  57. 2026-10-08 20:43 UTCEchelonGraph re-scored
  58. 2026-10-08 20:43 UTCVendor advisory
  59. 2026-10-08 20:42 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  60. 2026-10-08 17:14 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  61. 2026-10-08 07:56 UTCEchelonGraph re-scored
  62. 2026-10-08 07:56 UTCVendor advisory
  63. 2026-10-08 07:56 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  64. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  65. 2026-10-07 19:09 UTCVendor advisory
  66. 2026-10-07 19:09 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  67. 2026-10-07 06:21 UTCVendor advisory
  68. 2026-10-07 06:20 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  69. 2026-10-06 17:33 UTCEchelonGraph re-scored
  70. 2026-10-06 17:33 UTCVendor advisory
  71. 2026-10-06 17:33 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5
  72. 2026-10-06 15:19 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  73. 2026-10-06 04:47 UTCEchelonGraph re-scored
  74. 2026-10-06 04:47 UTCVendor advisory
  75. 2026-10-06 04:47 UTCGHSA enrichmentGHSA-rfp9-ffqc-h4x8 · GitHub severity HIGH · GitHub CVSS 7.5

Frequently asked(5)

What is CVE-2026-93990?
CVE-2026-93990 is a high-severity vulnerability; its CVE record was 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 made public?
CVE-2026-93990 was made public on September 18, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on September 19, 2026. EchelonGraph's copy of the record carries a last-modified date of November 10, 2026; the record at its source may have been updated since.
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 (36th 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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