# 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.


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 21 Oct 2026
- **Updated:** 22 Oct 2026
- **Also known as:** GHSA-wh9j-9gh8-wm87

## What is CVE-2026-112921?

CVE-2026-112921 is a vulnerability, published on 21 Oct 2026. 

### Official description

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.

Weakness: CWE-488 (Exposure of Data Element to Wrong Session)

## Which versions are affected by CVE-2026-112921?


## How do I fix CVE-2026-112921?

No fix has been published for CVE-2026-112921 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-112921 being exploited?

There is no known exploitation of CVE-2026-112921 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-112921 and fix it if it is affected.

What it is: CVE-2026-112921 is a vulnerability, published on 21 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-112921 in the wild and no public exploit code.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-112921/ (Markdown: https://insights.sbomify.com/CVE-2026-112921/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-112921
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-112921
- OSV: https://osv.dev/vulnerability/CVE-2026-112921

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-112921/
Summaries are generated and may contain mistakes; the official description above is the record.