🛡️ CVE-2026-43970 — cowlib

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-409 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Decompression Bomb in cow_spdy:inflate/2 Allows Memory Exhaustion via Crafted SPDY Frame

Summary

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.

Configuration

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. Rated impact: confidentiality none, integrity none, availability high.

Affected software

CVE-2026-43970 is recorded against 2 packages.

  • cowlib
  • unknown

Timeline and source

Published on 13 May 2026 and last revised on 30 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

cna.erlef.org (Web)
github.com (Fix)
hex.pm (Package)

CVE-2026-43970 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector 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
CWE CWE-409
Public Exploit ✅ No
Source NVD
Published 2026-05-13
Updated 2026-08-12
Modified 2026-07-30

Affected Packages

Software From version Fixed in
cowlib — —
unknown — —

Similar Threats

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