CVE-2026-38969: ruby webrick through v1.9.2 WEBrick reparses trailer Content-Length into canonical request state, enabling request smuggling.

highCVSS 7.5CVE-2026-38969

CSIRTS triage

vendor: Ruby product: webrickOtheraffected: v1.9.2

What: WEBrick reparses trailer Content-Length into canonical request state, enabling request smuggling.
Who is affected: Deployments using WEBrick up to version 1.9.2 are affected.
Urgency: Remediation is urgent due to the high severity and potential for exploitation.
Action: Upgrade WEBrick to a version beyond 1.9.2.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-07-02
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-38969

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-389690.29% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 21% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-38969	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

highCVE-2026-38969: ruby webrick through v1.9.2 WEBrick reparses trailer Content-Length into canonical request sta…nvd

Recent advisories for ruby webrick

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-38969: ruby webrick through v1.9.2 WEBrick reparses trailer Content-Length into canonical request sta…nvd · 2026-07-02