Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit…

Why it is Yellow

• CVSS 8.7 high
• Remotely exploitable without logging in

References

• https://cna.erlef.org/cves/CVE-2026-113436.html
• https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a
• https://github.com/mtrudel/bandit/commit/e0c8c0c30af9b0f57d8aafac37ddd9294363a8be
• https://github.com/mtrudel/bandit/security/advisories/GHSA-29cr-8477-rg6r
• https://osv.dev/vulnerability/EEF-CVE-2026-113436

Original description

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.