# CVE-2026-43970: Decompression Bomb in cow_spdy:inflate/2 Allows Memory Exhaustion via Crafted SPDY Frame

CVE-2026-43970 is fixed in erlang-cowlib on 1 platform by DEBIAN-CVE-2026-43970 (version 2.17.1-1), released May 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-43970
- Priority: Routine
- CVSS: n/a (Moderate)
- EPSS: 0.0051
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 13, 2026
- Weakness: Improper Handling of Highly Compressed Data (Data Amplification)
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43970

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | erlang-cowlib Debian 14 | 2.17.1-1 | [DEBIAN-CVE-2026-43970](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43970.md) | May 13, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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