Vulnerability advisory

GHSA-mc85-72gr-vm9f

Tesla has decompression bomb on response body

Published Jul 10, 2026Updated Jul 10, 2026OSV record ↗

Also known as CVE-2026-48594EEF-CVE-2026-48594

Severity

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

Affected versions

tesla Hex

All tesla advisories →

Affected Fixed in

0.6.0 to before 1.18.3 1.18.3Advisories →

Affected	Fixed in
`0.6.0` to before 1.18.3	`1.18.3`Advisories →
Also listed as affected (56) `0.10.0` `0.6.0` `0.7.0` `0.7.1` `0.7.2` `0.8.0` `0.9.0` `1.0.0` `1.0.0-beta.1` `1.1.0` `1.10.0` `1.10.1` `1.10.2` `1.10.3` `1.11.0` `1.11.1` `1.11.2` `1.12.0` `1.12.1` `1.12.2` `1.12.3` `1.13.0` `1.13.1` `1.13.2` `1.14.0` `1.14.1` `1.14.2` `1.14.3` `1.15.0` `1.15.1` `1.15.2` `1.15.3` `1.16.0` `1.17.0` `1.18.0` `1.18.1` `1.18.2` `1.2.0` `1.2.1` `1.3.0` `1.3.1` `1.3.2` `1.3.3` `1.4.0` `1.4.1` `1.4.2` `1.4.3` `1.4.4` `1.5.0` `1.5.1` `1.6.0` `1.6.1` `1.7.0` `1.8.0` `1.8.1` `1.9.0`

Also listed as affected (56)

Description

Summary

Any Tesla client pipeline that includes Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression eagerly decompresses HTTP response bodies with no size limit. A server under attacker control (or reached via a redirect) can return a tiny gzip-encoded payload that expands into gigabytes of BEAM heap, crashing or freezing the calling process. Stacking multiple content-encoding tokens multiplies the amplification exponentially.

Details

decompress_body/2 in lib/tesla/middleware/compression.ex passes the full response body to :zlib.gunzip/1 or :zlib.unzip/1 with no cap on output size. The list of codec tokens comes from splitting the content-encoding header on commas, and decompress_body/2 recurses once per token. A response advertising content-encoding: gzip, gzip, gzip, gzip triggers four recursive decompression passes. Each gzip layer can expand its input roughly 1000x, so a 284-byte wire payload with four layers inflates to approximately 1 GB at the innermost pass, all materialised as a single binary in the caller's heap.

PoC

Serve an HTTP response with content-encoding: gzip, gzip, gzip, gzip where the body is a 1 GB block of zeros compressed through four successive gzip passes.
Send that response to a Tesla client whose pipeline includes Tesla.Middleware.DecompressResponse.
decompress_body/2 recurses four times without any size check, materialising ~1 GB in the calling process's heap.
Repeated or sufficiently large requests exhaust available memory and crash or freeze the node.

Impact

High severity (CVSS v4.0: 8.2). Any application using tesla 0.6.0 through 1.18.2 with Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression in its pipeline is vulnerable. The attacker only needs to control a server the client contacts, including via redirects. Fixed in tesla 1.18.3.

Configurations

The application must include Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression in its Tesla middleware pipeline.

Resources

Introduction commit: https://github.com/elixir-tesla/tesla/commit/5bd90bb5cf0d15e375edc2a66fa322292940fce2
Patch commit: https://github.com/elixir-tesla/tesla/commit/340f75b5d191dc747ef7ac6365bd002d1cd55a9d