Bug 2477254 (CVE-2026-43970)

Summary: CVE-2026-43970 cowlib: cowlib: Remote denial of service via data amplification in SPDY frame processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in cowlib. This vulnerability, categorized as Improper Handling of Highly Compressed Data (Data Amplification), allows an unauthenticated remote attacker to cause a denial of service (DoS). By sending a specially crafted SPDY frame, the cow_spdy:inflate/2 function in cowlib passes highly compressed data to zlib:inflate/2 without proper size bounds. This can lead to excessive memory consumption, causing the affected system to run out of memory and crash.
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Bug Depends On: 2479811    
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Description OSIDB Bzimport 2026-05-13 20:02:48 UTC 
Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in ninenines cowlib allows unauthenticated remote denial of service via memory exhaustion.

cow_spdy:inflate/2 in cowlib passes peer-supplied compressed bytes directly to zlib:inflate/2 with no output size bound. The SPDY header compression dictionary (?ZDICT) is public, and zlib compresses long runs of repeated bytes at roughly 1024:1, so a few kilobytes of SPDY frame payload can decompress to gigabytes on the BEAM heap, OOM-killing the node. A single unauthenticated SPDY frame is sufficient to trigger the condition. The parsers for syn_stream, syn_reply, and headers frame types are all affected via cow_spdy:parse_headers/2.

This issue affects cowlib from 0.1.0 before 2.16.1.