Vulnerability · Published May 13, 2026 · Assigned by EEF
CVE-2026-43970Decompression Bomb in cow_spdy:inflate/2 Allows Memory Exhaustion via Crafted SPDY Frame
High 8.2
In plain English
A high-severity security flaw in cowlib from ninenines. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | erlang-cowlib | no fix listed | DEBIAN-CVE-2026-43970 |
| Debian:13 | erlang-cowlib | no fix listed | DEBIAN-CVE-2026-43970 |
| Debian:14 | erlang-cowlib | 2.17.1-1 | DEBIAN-CVE-2026-43970 |
| Ubuntu:22.04:LTS | erlang-cowlib | no fix listed | UBUNTU-CVE-2026-43970 |
| Ubuntu:24.04:LTS | erlang-cowlib | no fix listed | UBUNTU-CVE-2026-43970 |
| Ubuntu:25.10 | erlang-cowlib | no fix listed | UBUNTU-CVE-2026-43970 |
| Ubuntu:26.04:LTS | erlang-cowlib | no fix listed | UBUNTU-CVE-2026-43970 |
| Ubuntu:26.10 | erlang-cowlib | no fix listed | UBUNTU-CVE-2026-43970 |
Affected products (as reported)
Weakness: CWE-409 · 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