CVE-2026-18540

LOWPre-NVD 3.73.7—
EchelonGraph scoreMEDIUM confidence

This low-severity CVE scores 3.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 88% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — Patch released this week
3.7EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 3.7Exploit: None knownExposed: 0

A fix is available — apply it.

undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.

CVSS v3
3.7
EG Score
3.7(medium)
EG Risk
17(Track)
EG Risk 17/100SSVC: 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
Severity37% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
12%
KEV
Not listed

Published

September 4, 2026

Last Modified

September 8, 2026

References (2)

Vendor Advisories for CVE-2026-18540(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatgrafana12-4-main-12.4.10-0.2.hum12026-09-09redhat

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

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
node-undici5.15.0+dfsg1+~cs20.10.9.3-1 ... 8.9.0+dfsg+~cs3.2.0-1 (39 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
node-undici7.15.0+dfsg+~cs3.2.0-1 ... 8.9.0+dfsg+~cs3.2.0-1 (15 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
node-undici7.15.0+dfsg+~cs3.2.0-1 ... 8.9.0+dfsg+~cs3.2.0-1 (15 versions)——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 14× 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. 2026-09-11 14:52 UTCEPSS rescore
  2. 2026-09-11 14:12 UTCEG score recompute
  3. 2026-09-11 14:12 UTCVendor advisory
  4. 2026-09-11 09:36 UTCEPSS rescore
  5. 2026-09-10 09:34 UTCEPSS rescore
  6. 2026-09-08 22:00 UTCEPSS rescore
  7. 2026-09-08 19:56 UTCEG score recompute
  8. 2026-09-07 16:01 UTCEPSS rescore
  9. 2026-09-07 14:23 UTCEG score recompute
  10. 2026-09-06 13:47 UTCEPSS rescore
  11. 2026-09-04 18:34 UTCEG score recompute
  12. 2026-09-04 17:55 UTCEG score recompute
  13. 2026-09-04 17:20 UTCEG score recompute
  14. 2026-09-04 17:19 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-18540?
CVE-2026-18540 is a low vulnerability published on September 4, 2026. undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume…
When was CVE-2026-18540 disclosed?
CVE-2026-18540 was first published in the National Vulnerability Database on September 4, 2026, with the most recent update on September 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18540 actively exploited?
CVE-2026-18540 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 87.8% of all scored CVEs.
What is the CVSS score of CVE-2026-18540?
CVE-2026-18540 has a CVSS v3 base score of 3.7 (NVD).
How do I remediate CVE-2026-18540?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18540, 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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