PT-2026-39731 · Ninenines · Cowlib

Loïc Hoguin + 1 · Published 2026-05-11 · Updated 2026-05-11 · CVE-2026-7790

Mitre

CVSS v4.0

8.7

High

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow http te module) allows Excessive Allocation.

The chunked transfer-encoding parser in cow http te accepts an unbounded number of hex digits in the chunk-size field. Each digit causes a bignum multiplication (Len * 16 + digit), so parsing N hex digits requires O(N²) CPU work and O(N) memory. Additionally, when input is drip-fed, the parser discards the accumulated length on each partial read and restarts from zero on resumption, raising the cost to O(N³). An unauthenticated remote attacker can exploit this by sending an HTTP/1.1 request with Transfer-Encoding: chunked and a very long chunk-size hex string to cause denial of service through CPU exhaustion and memory amplification.

This vulnerability is associated with program file src/cow http te.erl and program routines cow http te:stream chunked/2, cow http te:chunked len/4.

This issue affects cowlib: from 0.6.0 before 2.16.1.

Fix

Resource Exhaustion

Weakness Enumeration

CWE-400

Related Identifiers

CVE-2026-7790

Affected Products

Cowlib

References · 4

• https://github.com/ninenines/cowlib/commit/a4b8039ce8c93ab00867ef6b7e888822c09f4369 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-7790 · Security Note
• https://cna.erlef.org/cves/CVE-2026-7790.html · Note
• https://osv.dev/vulnerability/EEF-CVE-2026-7790 · Note