Resource exhaustion in Ninenines Cowlib
CVE-2026-7790
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.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.008 (55.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 55.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.008 · change: +0.004
Affected products
- Ninenines Cowlib — versions 0.6.0, 8c0e428b012c59f553a264f285ed89d36f791e3e
Weakness classification (CWE)
References
- 6b3ad84c-e1a6-4bf7-a703-f496b71e49db (related, Third Party Advisory, third-party-advisory)
- 6b3ad84c-e1a6-4bf7-a703-f496b71e49db (related, Third Party Advisory)
- 6b3ad84c-e1a6-4bf7-a703-f496b71e49db (Patch, patch)
Frequently asked questions
- What is CVE-2026-7790?
- CVE-2026-7790 is a high-severity vulnerability in Ninenines Cowlib, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-05-11.
- How severe is CVE-2026-7790?
- High severity. CVSS v3 base score is 7.5 out of 10.