Bug 2469232 (CVE-2026-7790)

Summary: CVE-2026-7790 cowlib: cowlib: Denial of Service due to uncontrolled resource consumption in HTTP/1.1 chunked transfer-encoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in ninenines cowlib, specifically within the cow_http_te module's chunked transfer-encoding parser. An unauthenticated remote attacker can exploit this by sending an HTTP/1.1 request containing a Transfer-Encoding: chunked header with an excessively long hexadecimal string in the chunk-size field. This vulnerability, categorized as uncontrolled resource consumption, can lead to significant CPU exhaustion and memory amplification, ultimately causing a denial of service (DoS) on the affected system.
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Bug Depends On: 2484187    
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Description OSIDB Bzimport 2026-05-11 19:01:36 UTC 
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.