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.
- 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- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean?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? →
- Unclear
- 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
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).
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original 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.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- openwrt uhttpd
Version range not reported
References 3
GitHub · openwrt/uhttpd
Questions about CVE-2026-55612
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: github.com
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: github.com
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: 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 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: github.com