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TI-2026-83425 Aliases CVE-2026-55612

HTTP request smuggling in uhttpd via invalid chunk-length handling

Priority LOW 17CWE-444Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

uhttpd builds from commit b7c85a2819b3869279a669d5681f574824589c6c onward are affected before commit b78f518478794e16ba3568fc1258e40bf3e8eb3b and before commit 34460b8211d676ef1b9f40d6b775c5e112933690 (CWE-444). An invalid chunk length leaves unread body bytes that the keep-alive parser then handles as a new request on the same connection. A remote, unauthenticated attacker can use this to smuggle requests and desynchronize request boundaries.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0029 21st percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
openwrtuhttpd>= b7c85a2819b3869279a669d5681f574824589c6c, < b78f518478794e16ba3568fc1258e40bf3e8eb3b; >= b7c85a2819b3869279a669d5681f574824589c6c, < 34460b8211d676ef1b9f40d6b775c5e112933690—No fix listedCNA
  • uhttpd Vendoropenwrt Affected >= b7c85a2819b3869279a669d5681f574824589c6c, < b78f518478794e16ba3568fc1258e40bf3e8eb3b; >= b7c85a2819b3869279a669d5681f574824589c6c, < 34460b8211d676ef1b9f40d6b775c5e112933690 Fixed in — No fix listed CNA

Remediation

Commits b78f518478794e16ba3568fc1258e40bf3e8eb3b and 34460b8211d676ef1b9f40d6b775c5e112933690 patch the issue. The sources list no fixed version for uhttpd.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Timeline

  1. 2026-10-30 Threatist record created from CVE-2026-55612
  2. 2026-11-02 CISA SSVC decision points changed

References

Other 3

  • TI-2026-79903 Stack buffer overflow in odhcpd DHCPv6 IA reply handling CVSS 3.1CRITICAL 9.8
  • TI-2024-13053 Improper input validation in MediaTek MT6890, MT7915, MT7916, MT7981, MT7986 CVSS 3.1CRITICAL 9.8
  • TI-2026-79901 Use-after-free in odhcpd DHCPv6 IA handling CVSS 4.0HIGH 8.8
  • TI-2026-48502 OpenWrt luci-app-bmx7 Path Traversal via bmx7-info CVSS 4.0HIGH 8.7
  • TI-2026-44407 luci-app-banip Log Monitor IP Extraction Bypass CVSS 4.0HIGH 8.7
  • TI-2026-51067 luci-app-openvpn Path Traversal RCE via instance_name2 CVSS 4.0CRITICAL 9.4
See all 168 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences