libexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory.
CVE-2026-118370
HIGHNVD 8.28.2
EchelonGraph scoreMEDIUM confidence
“—” beside the score: it is equal to NVD's CVSS score.
This high-severity CVE scores 8.2 under NVD CVSS. EPSS exploit probability: 0.4% (33rd percentile of EPSS-scored CVEs). GitHub Security Advisory CVSS 5.9 is lower than this score; a lower GitHub score revises it only when its advisory is newer than the CVE record's last change, and this advisory (published 2026-10-28) is not newer than that change (2026-11-02), so it does not.
Triggered by: Headline CVSS from NVD CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS
Also known asEUVD-2026-111546 (ENISA EUVD) · GHSA-c6pw-vjr4-wwwr (GitHub Security Advisories)Source: ENISA EUVD
8.2EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 8.2Exploit: None knownExposed services: Not assessed
A fix is available — apply it.
- CVSS
- 8.2
- EG Score
- 8.2HIGHmedium confidence
- EG Risk
- 37EG Risk 37/100
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)Severity82% × 45%Impact severity (EG Severity): CVSS 8.2 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.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.Exploitation none (CISA Vulnrichment) · Automatable no (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. - EPSS PROB
- 0.4%
- EPSS %ILE
- 33rd
- 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 (8.2): severity, escalated by confirmed exploitation. This CVE's 8.2 is its impact severity (EG Severity), not escalated.
- EG Severity
- 8.2 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-10). 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 every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade 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 every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (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)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (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
October 28, 2026
Last Modified
November 2, 2026
Advisory Details (6)
Auto-updated Oct 28, 2026Patch available. Sources: github_pr, github_commit.
Web page
libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes | Advisories | VulnCheck
https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixesWeb 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/libexpatWeb page
libexpat/expat/lib/xmlparse.c at a76b1174c1ea52abb639a4c69d52b630a8a106a2 · libexpat/libexpat · GitHub
https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140GitHub commit
commit 621cb2c78b25 (libexpat/libexpat)
Fix landed in libexpat/libexpat commit 621cb2c78b25 — awaiting tagged release
https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04cGitHub commit
commit 1bac53c4fc46 (libexpat/libexpat)
Fix landed in libexpat/libexpat commit 1bac53c4fc46 — awaiting tagged release
https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750aeGitHub pull request
[CVE-REQUESTED] lib: Protect `attIndex` and `nPrefixes` in `storeAtts` from signed integer overflow
Upstream fix in progress (PR #1450 · libexpat/libexpat, state=open)
https://github.com/libexpat/libexpat/pull/1450Vendor Advisories for CVE-2026-118370(2)
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)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | — |
| — |
Alpine:v3.22(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | — |
| — |
Alpine:v3.23(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | — |
| — |
Alpine:v3.24(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | — |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | 2.10.0-1 ... 2.9.0-1~deb13u1 (37 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | 2.10.0-1 ... 2.9.0-1~deb13u1 (20 versions) |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| expat | 2.7.1-2 ... 2.9.0-1~deb13u1 (19 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 30× 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 → 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.
- 2026-11-13 16:50 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-11 16:38 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-11 03:44 UTCEchelonGraph re-scored
- 2026-11-11 03:44 UTCVendor advisory
- 2026-11-11 03:44 UTCGHSA enrichmentGHSA-c6pw-vjr4-wwwr · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-11-10 16:42 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-10 12:34 UTCEchelonGraph re-scored
- 2026-11-10 12:34 UTCGHSA enrichmentGHSA-c6pw-vjr4-wwwr · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-11-09 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-08 16:38 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-06 16:36 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-05 16:36 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-04 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-03 20:13 UTCEchelonGraph re-scored
- 2026-11-03 20:13 UTCVendor advisory
- 2026-11-03 20:13 UTCGHSA enrichmentGHSA-c6pw-vjr4-wwwr · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-11-03 16:46 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-11-02 20:26 UTCEchelonGraph re-scored
- 2026-11-02 20:26 UTCVendor advisory
- 2026-11-02 20:26 UTCGHSA enrichmentGHSA-c6pw-vjr4-wwwr · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-11-02 15:47 UTCEchelonGraph re-scored▲ 2.30
- 2026-11-02 15:47 UTCVendor advisory
Show 13 moreShow fewer
- 2026-11-02 15:47 UTCGHSA enrichmentGHSA-c6pw-vjr4-wwwr · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-11-02 15:46 UTCNVD updateCVSS → 8.2 · severity → HIGH
- 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-28 15:27 UTCEchelonGraph re-scored
- 2026-10-28 15:26 UTCGHSA enrichmentGHSA-c6pw-vjr4-wwwr · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-10-28 03:29 UTCEchelonGraph re-scored
- 2026-10-28 03:01 UTCENISA EUVD ID recordedEUVD-2026-111546 · Source: ENISA EUVD
- 2026-10-28 02:25 UTCEchelonGraph re-scoredFirst assessed: 5.9 MEDIUM
- 2026-10-28 02:24 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same CWE)
Same product
10 shownAlpine:v3.21:expat
- CVE-2024-45490EG 9.8CRITICAL
- CVE-2022-40674NVD 8.1EG 9.8CRITICAL
- CVE-2022-25315EG 9.8EPSS p92CRITICAL
- CVE-2022-25236EG 9.8EPSS p98CRITICAL
- CVE-2022-25235EG 9.8EPSS p92CRITICAL
- CVE-2022-23990NVD 7.5EG 9.8EPSS p92CRITICAL
- CVE-2022-23852EG 9.8EPSS p92CRITICAL
- CVE-2022-22824EG 9.8EPSS p90CRITICAL
- CVE-2022-22823EG 9.8EPSS p90CRITICAL
- CVE-2022-22822EG 9.8EPSS p93CRITICAL
Frequently asked(5)
What is CVE-2026-118370?
CVE-2026-118370 is a high-severity vulnerability; its CVE record was published on October 28, 2026. libexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document with a start tag carrying over 2^30 attributes to overflow…
When was CVE-2026-118370 made public?
CVE-2026-118370 was made public on October 27, 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 October 28, 2026. EchelonGraph's copy of the record carries a last-modified date of November 2, 2026; the record at its source may have been updated since.
Is CVE-2026-118370 actively exploited?
CVE-2026-118370 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (33rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-118370?
CVE-2026-118370 has a CVSS base score of 8.2 (NVD).
How do I remediate CVE-2026-118370?
A fix for CVE-2026-118370 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-118370 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-118370
Is Your Infrastructure Affected by CVE-2026-118370?
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