Quadratic bignum parsing of Content-Length and Host port values in Bandit
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-407.
Summary
Bandit, an Elixir HTTP server, is affected from 1.0.0-pre.7 before 1.14.0. Its header integer parser, Bandit.Headers.parse_integer/2, builds numbers one digit at a time without a digit limit, so a Content-Length or Host port value made of thousands of digits costs quadratic time to parse (CWE-407). An unauthenticated remote attacker can consume server CPU by sending such values over HTTP/1 or HTTP/2. Over HTTP/2, a value stored once in the HPACK dynamic table can be re-sent on each new stream for about one byte per stream.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a content-length value or a Host or :authority port made of thousands of digits. Bandit.Headers.parse_integer/2 in lib/bandit/headers.ex builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s. This issue affects bandit: from 1.0.0-pre.7 before 1.14.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Upgrade bandit to version 1.14.0 or later, which fixes this issue.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA bandit (mtrudel) Fixed in 1.14.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
mtrudel bandit 1.14.0, 220b9dfd27f9a21305be2afc75cbe585ddc24e7a
11 records Highest priority Priority MEDIUM 10 MEDIUM, 1 LOW
Other records, highest priority first
- TI-2026-80361 Bandit frames still reach WebSock after server-initiated closePriority MEDIUM 61
- TI-2026-80382 HTTP/2 frames let clients hold Bandit request body reads openPriority MEDIUM 45
- TI-2026-80371 WebSocket 1-byte continuation frames exhaust memory in BanditPriority MEDIUM 45
Timeline
- 2026-10-26 Threatist record created from CVE-2026-113436
- 2026-10-26 CISA SSVC decision points changed
References
More mtrudel vulnerabilities
- TI-2026-81989 HTTP/2 request bodies made of 1-byte DATA frames amplify memory use in Bandit CVSS 4.0HIGH 8.7
- TI-2026-74311 Bandit HTTP/2 send timers reset, letting trickles pin stream processes CVSS 4.0HIGH 8.7
- TI-2026-52571 HTTP/2 connection-window starvation pins Plug processes indefinitely in Bandit CVSS 4.0HIGH 8.7
- TI-2026-46780 Quadratic CPU blow-up reassembling fragmented WebSocket messages in Bandit CVSS 4.0HIGH 8.7
- TI-2026-31007 WebSocket fragmented message reassembly unbounded in bandit CVSS 4.0HIGH 8.7
- TI-2026-28689 HTTP/1 chunked decoder infinite loop on requests with trailer fields in bandit CVSS 4.0HIGH 8.7
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences