Vulnerability advisory

CVE-2026-7790

Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS

Published May 11, 2026Updated Oct 28, 2026OSV record ↗

Also known as EEF-CVE-2026-7790GHSA-32p9-57cr-4x65

Severity

CVSS 4.0CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Affected versions

Repository

Affected commits	Fixed by commit
GIT github.com/ninenines/cowlib ↗
a6626f3b4539b07366034b4953ab2df29e3a9d58 to before bae6b022af54566f3518a3aa59083b4591d552de	`bae6b022af54566f3518a3aa59083b4591d552de`
Not specified	`a4b8039ce8c93ab00867ef6b7e888822c09f4369`
Also listed as affected (36) `2.16.0` `2.15.0` `2.14.0` `2.13.0` `2.12.1` `2.12.0` `2.11.0` `2.10.1` `2.10.0` `2.9.1` `2.9.0` `2.8.0` `2.7.3` `2.7.2` `2.7.1` `2.7.0` `2.6.0` `2.5.1` `2.5.0` `2.4.0` `2.3.0` `2.2.1` `2.2.0` `2.1.0` `2.0.1` `2.0.0` `2.0.0-rc.1` `2.0.0-pre.1` `1.0.1` `1.3.0` `1.2.0` `1.1.0` `1.0.0` `0.6.2` `0.6.1` `0.6.0`

Description

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.

CVE-2026-7790

Affected versions

Repository

Description

References