# CVE-2026-86219

## Summary

- **CVE ID:** CVE-2026-86219
- **Severity:** CRITICAL
- **CVSS Score:** 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** CWE-294
- **Published:** Sep 6, 2026
- **Last Modified:** Sep 8, 2026

## Description

Authen::SASL::Perl::DIGEST_MD5 versions before 2.2100 for Perl accept replayed authentication responses via unverified nonce in server_step.

server_start generates a fresh nonce and sends it in the challenge, and nothing later compares that value against the nonce the client returns. server_step derives the expected digest from the client's own parameters, so a response verifies whenever its digest matches the nonce it carries. The count table it also checks is keyed on the client-supplied nonce and starts empty in each new server object, so a captured first response, carrying `nc=00000001`, passes that too. RFC 2831 defines the nonce in the response as the value the server sent in the preceding challenge.

An attacker who observes one successful `qop=auth` exchange can replay the captured response against a later session for the same service, host, realm and user, and authenticate as that user without knowing the password.

## Affected Products

- Unknown product (0)

## References

- [CNA](https://metacpan.org/release/EHUELS/Authen-SASL-2.2000/source/lib/Authen/SASL/Perl/DIGEST_MD5.pm#L203-222)
- [CNA](https://metacpan.org/release/EHUELS/Authen-SASL-2.2000/source/lib/Authen/SASL/Perl/DIGEST_MD5.pm#L410-414)
- [CNA](https://datatracker.ietf.org/doc/html/rfc2831#section-2.1.2)
- [CNA](https://github.com/perl-authen-sasl/perl-authen-sasl/commit/94337367030612842924f697cead29964a96448d.patch)
- [CNA](https://metacpan.org/release/EHUELS/Authen-SASL-2.2100/changes)
- [CNA](https://www.cve.org/CVERecord?id=CVE-2025-40918)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.49%
- **EPSS Percentile:** 40.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._