Ladybird: FinalizationRegistry::cleanup() heap use-after-free via reentrant unregister()
Affects Ladybird builds through commit 8121ff82 on main (May 2026), where FinalizationRegistry cleanup can use freed memory. No vendor severity is given. Fixed by commit 209579c.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Ladybird, an independent web browser, is affected by a memory-safety flaw in its JavaScript engine's FinalizationRegistry cleanup logic. The bug can crash the browser's web content process and could potentially allow memory corruption, with the impact fixed in a later commit.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
Ladybird is a truly independent web browser. Prior to 209579c96473c75bd5eba9701fcadb841a045964, FinalizationRegistry::cleanup() in Libraries/LibJS/Runtime/FinalizationRegistry.cpp removed a dead record from m_records, retained an iterator to the next FinalizationRecord, and then invoked attacker-controlled JavaScript through the cleanup callback. If that callback called unregister() for the next record, remove_by_token() freed the node referenced by the retained iterator, and the next cleanup iteration read its target and held_value fields after free. This reliably crashes instrumented WebContent builds and creates a memory-corruption primitive in production builds. This vulnerability is fixed by commit 209579c96473c75bd5eba9701fcadb841a045964.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- LadybirdBrowser ladybird
Version range not reported
References 2
GitHub · LadybirdBrowser/ladybird
Questions about CVE-2026-119332
What does this mean?
During cleanup of a FinalizationRegistry, a cleanup callback that calls unregister() on the next dead record's token can free a node the iterator still points to. Using that freed memory is a heap use-after-free.Source: github.com
Am I affected, and how do I check?
The listed affected builds are Ladybird main through commit 8121ff82 (May 2026). To check a build, compare its commit against 8121ff82; the affected setup is a FinalizationRegistry cleanup callback that calls unregister() on the next record's token.Source: github.com
What should I do about it?
Update to a Ladybird build that includes commit 209579c, which is the listed fix. The sources checked do not name a release version containing that commit.Source: github.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What if there's no patch?
The sources checked do not describe a workaround. Until a build with commit 209579c is used, avoid calling unregister() on the next record's token from within a FinalizationRegistry cleanup callback, which is the triggering pattern.Source: github.com