# CVE-2026-77781: Tie::Hash::Regex versions before 2.0.0 for Perl will throw an exception on unparseable lookup keys

> An attacker can cause a denial of service by supplying malformed regex keys to a Perl application using Tie::Hash::Regex, triggering an unhandled exception.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-77781, GHSA-fwmp-gxj5-29mj, UBUNTU-CVE-2026-77781

## What is CVE-2026-77781?

CVE-2026-77781 is a high-severity denial of service vulnerability, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Tie::Hash::Regex versions before 2.0.0 for Perl will throw an exception on unparseable lookup keys.

The FETCH, EXISTS and DELETE methods throw an exception when on malformed regular expressions.

Each method falls back to a regex match when the key is not already stored in the hash, compiling the caller's key with a bare qr// and no eval guard. A key that is not a valid regular expression pattern, such as a single unmatched bracket, dies.

An application that looks up externally supplied strings in a tied hash will die on an invalid key.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-77781?


## How do I fix CVE-2026-77781?

Upgrade to a fixed version.

## Is CVE-2026-77781 being exploited?

There is no known exploitation of CVE-2026-77781 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77781 and fix it if it is affected.

What it is: CVE-2026-77781 is a high-severity denial of service vulnerability, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77781 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-2026-77781/ (Markdown: https://insights.sbomify.com/CVE-2026-77781/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77781
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77781
- OSV: https://osv.dev/vulnerability/CVE-2026-77781

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77781/
Summaries are generated and may contain mistakes; the official description above is the record.