Weakness Type (CWE)

CWE-409 — CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)

CAPEC

CVSS 4.0 Score

8.2

HIGH

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

Vulnerability description

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.

Affected

pkg:hex/cowlib

Module Source File Routine
cow_spdy src/cow_spdy.erl cow_spdy:parse/2
cow_spdy:inflate/2
cow_spdy:parse_headers/2
cow_spdy:parse_headers/4
Status Type Version Changes / Fixed in
affected semver ⓘ 0.1.0 < 2.16.1

pkg:github/ninenines/cowlib

Module Source File Routine
cow_spdy src/cow_spdy.erl cow_spdy:parse/2
cow_spdy:inflate/2
cow_spdy:parse_headers/2
cow_spdy:parse_headers/4
Status Type Version Changes / Fixed in
affected git ⓘ fad5c0049d < 16aad3fb9f

Configurations

The application must use cow_spdy:parse/2 to parse SPDY frames from an untrusted peer. cowboy itself does not use cow_spdy; only direct callers of the cow_spdy API are affected.

Solutions

Upgrade to cowlib 2.16.1 or later, in which the cow_spdy module has been removed entirely. No patched version of cow_spdy will be provided. Migrate away from SPDY, which has been deprecated since 2015 in favour of HTTP/2.

References

Credits

  • Finder: Peter Ullrich
  • Remediation developer: Loïc Hoguin

CVE record as JSON:  GET /cves/CVE-2026-43970.json
OSV record as JSON:  GET /osv/EEF-CVE-2026-43970.json