Decompression bomb in Tesla.Middleware.DecompressResponse and Tesla.Middleware.Compression

Weakness Type (CWE)

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

CAPEC

CAPEC-130 — CAPEC-130 Excessive Allocation

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 elixir-tesla tesla allows a denial of service via decompression bomb in HTTP response bodies.

When Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression is included in a Tesla middleware pipeline, HTTP response bodies are decompressed eagerly with no size limit. The decompress_body/2 function in lib/tesla/middleware/compression.ex passes the entire response body to :zlib.gunzip/1 or :zlib.unzip/1 without any cap on the output size. Additionally, compression_algorithms/1 splits the content-encoding header on commas and decompress_body/2 recurses once per token, applying a decompression pass on each iteration. A server advertising content-encoding: gzip, gzip, gzip, gzip causes four recursive decompression passes, yielding exponential amplification: each gzip layer can expand its input roughly 1000x, so a payload of a few hundred bytes on the wire inflates to gigabytes of BEAM heap, exhausting memory and crashing or freezing the calling process.

This issue affects tesla: from 0.6.0 before 1.18.3.

Affected

`pkg:hex/tesla`

Module	Source File	Routine
`Tesla.Middleware.Compression`	`lib/tesla/middleware/compression.ex`	`Tesla.Middleware.DecompressResponse.call/3`
`Tesla.Middleware.DecompressResponse`		`Tesla.Middleware.Compression.call/3`

Status	Type	Version	Changes / Fixed in
affected	semver ^ⓘ	`0.6.0`	< `1.18.3`

`pkg:github/elixir-tesla/tesla`

Module	Source File	Routine
`Tesla.Middleware.Compression`	`lib/tesla/middleware/compression.ex`	`Tesla.Middleware.DecompressResponse.call/3`
`Tesla.Middleware.DecompressResponse`		`Tesla.Middleware.Compression.call/3`

Status	Type	Version	Changes / Fixed in
affected	git ^ⓘ	`5bd90bb5cf`	< `340f75b5d1`

Configurations

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

References

https://github.com/elixir-tesla/tesla/security/advisories/GHSA-mc85-72gr-vm9f vendor-advisory related
https://osv.dev/vulnerability/EEF-CVE-2026-48594 related
https://github.com/elixir-tesla/tesla/commit/340f75b5d191dc747ef7ac6365bd002d1cd55a9d patch

Credits

Finder: Peter Ullrich
Remediation developer: Yordis Prieto
Analyst: Jonatan Männchen

CVE record as JSON: GET /cves/CVE-2026-48594.json
OSV record as JSON: GET /osv/EEF-CVE-2026-48594.json