What’s Vulnerable › Vulnerabilities

CVE-2026-111101: HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use in Bandit

• Severity: high (CVSS 8.7 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-26 · updated 2026-10-26
• Weakness: CWE-770

Description

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory and CPU via a request body made of many 1-byte chunks. The chunked reader in lib/bandit/http1/socket.ex keeps every chunk as its own list cell and binary term until IO.iodata_to_binary/1 joins them, and nothing limits the number of chunks. The :length option of read_body/2 counts only data bytes, so tiny chunks cost far more memory than their payload: 48 MB of 1-byte chunks grew one handler process to about 500 MB and took about 6 s of CPU. The route does not need to read the body, because on keep-alive connections ensure_completed/1 drains unread bodies through the same reader. This issue affects bandit: from 0.1.0 before 1.14.0.

Affected products

• mtrudel bandit: from 0.1.0 before 1.14.0 — fixed in 1.14.0

How to fix

Upgrade to a fixed version: mtrudel bandit 1.14.0. Check the vendor advisory for mitigations.

References

• https://cna.erlef.org/cves/CVE-2026-111101.html
• https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a
• https://github.com/mtrudel/bandit/commit/7201270c34b90f6c9e15c0386c2bb802c0c72ab4
• https://github.com/mtrudel/bandit/security/advisories/GHSA-jwh3-j29h-qfmw
• https://osv.dev/vulnerability/EEF-CVE-2026-111101

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