CVE-2026-124040

HIGHPre-NVD 8.18.1
EchelonGraph scoreHIGH confidence

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

Score 8.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-11-06. A secondary CVSS source baseline 8.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source

Also known asEUVD-2026-118441 (ENISA EUVD) · GHSA-wj2x-x5pc-4h8r (GitHub Security Advisories)Source: ENISA EUVD

8.1EG
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: 0.5%CVSS: 8.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

CivetWeb through 1.16, when built with USE_HTTP2 and enable_http2 on, contains a use-after-free vulnerability in handle_http2() that retains freed :method and :path pointers. Unauthenticated remote attackers can send a later HEADERS frame omitting these pseudo-headers to influence request method or path seen by access rules, or crash the server.

CVSS v3
8.1
EG Score
8.1HIGHhigh confidence
EG Risk
37
EG 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)
Severity81% × 45%
Impact severity (EG Severity): CVSS 8.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.5% × 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 low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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
0.5%
EPSS %ILE
44th
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 (8.1): severity, escalated by confirmed exploitation. This CVE's 8.1 is its impact severity (EG Severity), not escalated.

EG Severity
8.1 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.5% 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 low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 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 low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; 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 total (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

November 6, 2026

Last Modified

November 11, 2026

Advisory Details (4)

Auto-updated Nov 6, 2026
🔬 Proof of concept available. Patch available.
Web page

CivetWeb through 1.16 HTTP/2 Use-After-Free via Stale Pseudo-Header State | Advisories | VulnCheck

https://www.vulncheck.com/advisories/civetweb-through-1.16-http-2-use-after-free-via-stale-pseudo-header-state
Web page

civetweb/src/http2.inl at v1.16 · civetweb/civetweb · GitHub

https://github.com/civetweb/civetweb/blob/v1.16/src/http2.inl#L1574-L1581
Web page

GitHub - civetweb/civetweb: Embedded C/C++ web server · GitHub

https://github.com/civetweb/civetweb
Web page🟡 PoC Available

Security: multiple suspected server-side memory-safety issues in WebSocket and HTTP/2 paths · Issue #1379 · civetweb/civetweb · GitHub

https://github.com/civetweb/civetweb/issues/1379

Vendor Advisories for CVE-2026-124040(2)

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

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
civetweb1.15+dfsg-4 ... 1.16+dfsg-6 (7 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
civetweb1.16+dfsg-2 ... 1.16+dfsg-6 (6 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
civetweb1.16+dfsg-2, 1.16+dfsg-3, 1.16+dfsg-4, 1.16+dfsg-5, 1.16+dfsg-6
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 12× 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.

  1. 2026-11-13 16:50 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  2. 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  3. 2026-11-11 16:38 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  4. 2026-11-11 05:28 UTCEchelonGraph re-scored
  5. 2026-11-11 05:28 UTCGHSA enrichmentGHSA-wj2x-x5pc-4h8r · GitHub severity CRITICAL · GitHub CVSS 8.1
  6. 2026-11-11 03:30 UTCEchelonGraph re-scored
  7. 2026-11-11 03:30 UTCGHSA enrichmentGHSA-wj2x-x5pc-4h8r · GitHub severity CRITICAL · GitHub CVSS 8.1
  8. 2026-11-10 16:42 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  9. 2026-11-09 16:34 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  10. 2026-11-08 16:38 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  11. 2026-11-08 08:52 UTCEchelonGraph re-scored
  12. 2026-11-08 08:52 UTCGHSA enrichmentGHSA-wj2x-x5pc-4h8r · GitHub severity CRITICAL · GitHub CVSS 8.1
  13. 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  14. 2026-11-06 20:27 UTCEchelonGraph re-scored
  15. 2026-11-06 20:04 UTCENISA EUVD ID recordedEUVD-2026-118441 · Source: ENISA EUVD
  16. 2026-11-06 19:22 UTCEchelonGraph re-scoredFirst assessed: 8.1 HIGH
  17. 2026-11-06 19:22 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-124040?
CVE-2026-124040 is a high-severity vulnerability; its CVE record was published on November 6, 2026. CivetWeb through 1.16, when built with USE_HTTP2 and enable_http2 on, contains a use-after-free vulnerability in handle_http2() that retains freed :method and :path pointers. Unauthenticated remote attackers can send a later HEADERS frame omitting these pseudo-headers to influence request method or…
When was CVE-2026-124040 made public?
CVE-2026-124040 was made public on March 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 November 6, 2026. EchelonGraph's copy of the record carries a last-modified date of November 11, 2026; the record at its source may have been updated since.
Is CVE-2026-124040 actively exploited?
CVE-2026-124040 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (44th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-124040?
CVE-2026-124040 has a CVSS base score of 8.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-124040?
A fix for CVE-2026-124040 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-124040 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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