# CVE-2026-128242: actix-http before 3.20.1 and actix-web before 4.18.2 Decompression Bomb DoS via encoding::Decoder

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

actix-http before 3.20.1 and actix-web before 4.18.2 contain an unbounded decompression vulnerability in encoding::Decoder that lets remote attackers exhaust memory and CPU via compressed bodies. Attackers can send small highly compressed gzip, deflate, Brotli or zstd request bodies to Json, Form, Bytes or String extractors, or serve them to awc clients, causing denial of service.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/actix/actix-web/commit/41b54d23ea04f66758c15de7e4ab18325cd25280
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/actix/actix-web/commit/0d0be61bd757027bfcecbc53df1b7a600f21ecd0

## Affected products and versions

- actix / actix-http (actix-http): ≥ 0; < 3.20.1 (affected, semver). Source: CNA: VulnCheck
- actix / actix-web (actix-web): ≥ 0; < 4.18.2 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-409

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/actix/actix-web/security/advisories/GHSA-qph8-7859-gq2f (CNA: VulnCheck; vendor-advisory)

- https://rustsec.org/advisories/RUSTSEC-2026-0448.html (CNA: VulnCheck; third-party-advisory)

- https://github.com/actix/actix-web/commit/41b54d23ea04f66758c15de7e4ab18325cd25280 (CNA: VulnCheck; patch)

- https://github.com/actix/actix-web/commit/0d0be61bd757027bfcecbc53df1b7a600f21ecd0 (CNA: VulnCheck; patch)

- https://github.com/actix/actix-web/blob/actix-http-v3.20.0/actix-http/src/encoding/decoder.rs#L239-L301 (CNA: VulnCheck; technical-description)

- https://github.com/actix/actix-web/releases/tag/actix-http-v3.20.1 (CNA: VulnCheck; release-notes)

- https://github.com/actix/actix-web/releases/tag/actix-web-v4.18.2 (CNA: VulnCheck; release-notes)

- https://github.com/actix/actix-web (CNA: VulnCheck; product)

- https://www.vulncheck.com/advisories/actix-http-before-3.20.1-and-actix-web-before-4.18.2-decompression-bomb-dos-via-encoding-decoder (CNA: VulnCheck; third-party-advisory)

- https://github.com/actix/actix-web (disclosure@vulncheck.com)

- https://github.com/actix/actix-web/blob/actix-http-v3.20.0/actix-http/src/encoding/decoder.rs#L239-L301 (disclosure@vulncheck.com)

- https://github.com/actix/actix-web/commit/0d0be61bd757027bfcecbc53df1b7a600f21ecd0 (disclosure@vulncheck.com)

- https://github.com/actix/actix-web/commit/41b54d23ea04f66758c15de7e4ab18325cd25280 (disclosure@vulncheck.com)

- https://github.com/actix/actix-web/releases/tag/actix-http-v3.20.1 (disclosure@vulncheck.com)

- https://github.com/actix/actix-web/releases/tag/actix-web-v4.18.2 (disclosure@vulncheck.com)

- https://github.com/actix/actix-web/security/advisories/GHSA-qph8-7859-gq2f (disclosure@vulncheck.com)

- https://rustsec.org/advisories/RUSTSEC-2026-0448.html (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/actix-http-before-3.20.1-and-actix-web-before-4.18.2-decompression-bomb-dos-via-encoding-decoder (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-128242; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-128242; retrieved 2026-11-13; source updated 2026-11-13

Revision: 7a7e239ffd67d1af1d267a57f70bcb9c65e02ebd75fa9b950ecd945f3b54ecdf

Canonical: https://y2.dev/cve/CVE-2026-128242

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