CVE-2026-8927: When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. S

criticalCVSS 9.1CVE-2026-8927

When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. Specifically, if the initial transfer authenticates against proxyA using Digest auth, a subsequent transfer routed through proxyB erroneously leaks the Proxy-Authorization: header intended solely for proxyA.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: critical — CVSS 9.1
Published: 2026-07-03
Last updated: 2026-07-07
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-8927

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-2026-89270.75% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 51% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-8927	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

medium[UPDATE] [medium] cURL: Multiple vulnerabilitiescert-bund
mediumCVE-2026-8927: env-set cross-proxy Digest auth state leakmsrc
unknownMultiple vulnerabilities in cURL and libcurl (June 24, 2026)cert-fr-avis

Recent advisories for When reusing a

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.

unknownCVE-2026-23556: When oxenstored is tearing a domain down, the node data is cleaned up but the usage counts are…nvd · 2026-07-09
highCVE-2026-28740: Gitea versions up to and including 1.26.2 allow Git LFS object reuse to authorize private sour…nvd · 2026-07-03
highCVE-2026-27775: Gitea 1.25.5 caches a branch-specific write-permission result across multiple refs in one pre-…nvd · 2026-07-03
highCVE-2026-8932: libcurl would reuse a previously created connection even when some mTLS config related option h…nvd · 2026-07-03
mediumCVE-2026-8458: libcurl might in some circumstances reuse the wrong connection when asked to do Negotiate-authe…nvd · 2026-07-03
highCVE-2026-8286: A vulnerability exists where a new transfer that uses STARTTLS to upgrade the connection might …nvd · 2026-07-03