What is CVE-2026-75922?
Reverse::Proxy versions before 0.04 for Perl allow HTTP request smuggling via a percent-decoded PATH_INFO written unencoded to the upstream request line. PSGI hands PATH_INFO to an application percent-decoded, so a %XX sequence in the client URL has become a raw byte by the time the proxy sees it. The proxy appends that byte string to the upstream base URL, and for an Upgrade tunnel writes it into a request line it serializes itself, re-encoding nothing in either path. The HTTP client that sends the resulting URL does not validate the target either. A path containing %0d%0a therefore arrives at the upstream as a CRLF that ends the request line, and a decoded space, '?' or '#' truncates it the same way. Everything the client writes after the CRLF is read by the upstream as a second request. On the buffered path it arrives on a keep-alive connection the proxy pools and reuses for other clients. Its method, path and headers are all chosen by the client, and the upstream attributes it to the proxy, so it reaches upstream paths that the proxy's own routing does not expose.
The record classifies CVE-2026-75922 under weakness classes CWE-444, CWE-93. The identifier was first published 43 days ago.
Severity and exploitation probability
- EPSS (FIRST)
- 0.2% probability of exploitation in the next 30 days, higher than 17.6% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 0.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-08-23
Is CVE-2026-75922 being exploited?
It currently carries a trending score of 34 in the Threadlinqs vulnerability feed.
Affected products and versions
No affected-product or package list has been recorded for CVE-2026-75922 in the tracked sources. The vendor advisory and the references below are the authoritative statement of what is affected.
How to fix CVE-2026-75922
No vendor patch reference has been recorded for CVE-2026-75922 in the tracked sources. Follow the references below for a fix, and treat any affected deployment as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-75922
No threat campaign in the Threadlinqs corpus currently references CVE-2026-75922, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.
Sources
Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.