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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-77781?
How do I fix CVE-2026-77781?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-77781 being exploited?
There is no known exploitation of CVE-2026-77781 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-77781, GHSA-fwmp-gxj5-29mj, UBUNTU-CVE-2026-77781.