# CVE-2026-119235: proxygen QPACK decoder unbounded buffering denial of service

Source: https://junglewise.ai/threats/cve-2026-119235-proxygen-s-qpack-decoder-enforced-its-size-limit-on-a-string  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-119235 · Severity: info · Published 2026-11-11

proxygen is an HTTP/3 protocol library used in Meta's infrastructure. A remote attacker can send specially crafted HTTP/3 messages that cause the QPACK decoder to buffer arbitrarily large amounts of data, exhausting server memory and causing denial of service without authentication.

Technologies: [Meta Proxygen](https://junglewise.ai/threats/technologies/meta-proxygen). Vendors: [Meta](https://junglewise.ai/threats/vendors/meta).

## Quick answers

**Is CVE-2026-119235 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-119235 being exploited in the wild.

**How severe is CVE-2026-119235?** Informational severity, published 11 November 2026.

**Which products and versions are affected?** Meta Proxygen before v2026.11.09.00.

**Is there a fix for CVE-2026-119235?** Yes: fixed in proxygen v2026.11.09.00. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-119235 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-119235?** Check whether you run Meta Proxygen at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in proxygen v2026.11.09.00

## Technical details

The QPACK decoder fails to enforce size limits on string literals in encoder-stream instructions until after the entire literal has been received. An attacker can declare an arbitrarily large literal size and continuously send data, causing unbounded buffering for the connection lifetime. This bypasses normal size restrictions regardless of dynamic table capacity settings.

## Affected products

- Meta proxygen before v2026.11.09.00

## Timeline

- 2026-11-11: advisory

## References

- [https://github.com/meta/proxygen/commit/daf245bba7fe1304b9491403fe56f91153299781](https://github.com/meta/proxygen/commit/daf245bba7fe1304b9491403fe56f91153299781)
- [https://www.facebook.com/security/advisories/cve-2026-119235](https://www.facebook.com/security/advisories/cve-2026-119235)

## Related threats

- [Meta proxygen use-after-free in HTTP session handling](https://junglewise.ai/threats/cve-2026-121737-when-a-remote-unauthenticated-http-1-1-client-pipelined-the)
- [Meta proxygen HTTP/3 denial of service in QPACK handling](https://junglewise.ai/threats/cve-2026-119237-in-proxygen-s-http-3-session-when-a-headers-block-referenced)
- [Meta proxygen HTTP/3 denial of service in frame buffering](https://junglewise.ai/threats/cve-2026-119233-proxygen-s-http-3-codec-buffered-an-incomplete-non-data-frame)
- [Meta proxygen use-after-free in stream cleanup](https://junglewise.ai/threats/cve-2026-91096-in-proxygen-from-v2024-10-28-00-until-v2026-09-28-00)
- [Meta proxygen use-after-free in WebTransport stream handling](https://junglewise.ai/threats/cve-2026-91095-in-proxygen-from-v2024-10-28-00-until-v2026-09-28-00-the)