Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-112921
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-21 22:16:48 UTC
Updated2026-10-21 22:16:48 UTC
DescriptionRobots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request. Each Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client's address is then checked against the robot's DNS rule, which it fails. A remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated. Note that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug.

Risk And Classification

Problem Types: CWE-488 | CWE-488 CWE-488 Exposure of Data Element to Wrong Session

References

ReferenceSourceLinkTags
metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d500... 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Solutions

CNA: Upgrade to Robots-Validate v0.4.10 or later. Deployments with Algorithm::AhoCorasick::XS should upgrade to v0.4.11, which fixed a bug with using that version.

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