# CVE-2026-116135: HTTP::Body versions before 1.23_01 for Perl drop mixed-case percent escapes from urlencoded form fields instead of decoding them

Status: published. Published: 2026-10-28. Updated: 2026-11-05.

HTTP::Body versions before 1.23_01 for Perl drop mixed-case percent escapes from urlencoded form fields instead of decoding them.

The decode table holds only the all-lowercase and all-uppercase spelling of each hex pair, while the escape pattern matches either case. An escape such as %aB finds no entry and is replaced with nothing, joining the bytes on either side. Hex digits in percent escapes are case-insensitive, and conforming decoders return the byte.

A remote attacker can send a field name or value that a conforming decoder in front of the application reads differently, so that pass%aBword reaches the application as password.

## Remediation

- fix: Upgrade to HTTP-Body 1.23_01 or later. (source: CNA: CPANSec)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: CPANSec) — https://github.com/libwww-perl/HTTP-Body/commit/336f1a23b4115a5cbeb546f36df5af62c90bdc0d.patch

## Affected products and versions

-  /  (HTTP-Body): ≥ 0; < 1.23_01 (affected, custom). Source: CNA: CPANSec

## Severity and prioritization

- CVSS 3.1: 9.8 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: ADP: CISA-ADP

- CISA KEV: No listing in collected sources

- EPSS: 0.34% as of 2026-11-05; percentile 27.81%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-178

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/libwww-perl/HTTP-Body/commit/336f1a23b4115a5cbeb546f36df5af62c90bdc0d.patch (CNA: CPANSec; patch)

- https://metacpan.org/release/GETTY/HTTP-Body-1.24/changes (CNA: CPANSec; release-notes)

- https://www.rfc-editor.org/rfc/rfc3986#section-2.1 (CNA: CPANSec)

## Provenance

- CNA: CPANSec: https://www.cve.org/CVERecord?id=CVE-2026-116135; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-116135; retrieved 2026-11-05; source updated Not reported

Revision: 181c8b1fa7752a7a90bcc2168dad0b00dd64965d18f86bb59d900a7fd27f3f09

Canonical: https://y2.dev/cve/CVE-2026-116135

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