UNKNOWN NVD
CVE-2026-112921
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
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.
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.
References
- https://github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d5006ef384402.
- https://metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes
- https://metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes
- https://www.openwall.com/lists/oss-security/2026/10/21/30
This unknown severity vulnerability was published on 2026-10-21 via NVD.
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