# CVE-2026-65627: Decompression bomb via unbounded zlib:inflate in jose_jwe_zip:uncompress/2

Status: published. Published: 2026-10-26. Updated: 2026-11-02.

Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in potatosalad jose (erlang-jose) allows a remote attacker to exhaust a node's memory with a small crafted JWE token.

The jose_jwe_zip:uncompress/2 function in src/jwe/jose_jwe_zip.erl decompresses the DEFLATE-compressed plaintext of a JWE that carries the optional zip: DEF header by calling zlib:inflate/2 on the entire attacker-controlled stream, with no bound on the output size or the inflation ratio. Raw DEFLATE reaches ratios around 1000:1 on highly repetitive input, so a few-kilobyte token inflates to hundreds of megabytes or gigabytes in a single call.

Decompression runs automatically during decryption through jose_jwe:block_decrypt/2 (JOSE.JWE.block_decrypt/2 in Elixir), before the recipient can inspect or reject the payload. With the common asymmetric key-management algorithms (RSA-OAEP, ECDH-ES) an attacker needs only the recipient's public key to craft such a token, so no authentication or secret material is required. A single small token can exhaust the node's memory and crash the BEAM, denying service to all users.

This issue affects jose: from 1.0.0 before 1.11.13.

## Remediation

- workaround: Reject JWE tokens that carry a zip header before passing them to jose_jwe:block_decrypt/2. DEFLATE compression is rarely used in legitimate JWE traffic, so untrusted tokens whose protected header contains zip: DEF can be inspected and filtered out before decryption. (source: CNA: EEF)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/potatosalad/erlang-jose/commit/857eb8e7f2d33e2c9ca2189e77226561cacaf2ad

## Affected products and versions

- potatosalad / jose (jose): ≥ 1.0.0; < 1.11.13 (affected, semver). Source: CNA: EEF
- potatosalad / jose (potatosalad/erlang-jose): ≥ a7746ecd4950f85a393136e449a91dac62b5c429; < 857eb8e7f2d33e2c9ca2189e77226561cacaf2ad (affected, git). Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: EEF

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:L/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: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

- CISA KEV: No listing in collected sources

- EPSS: 0.25% as of 2026-11-02; percentile 16.21%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-409

## Exploit evidence

- exploit: https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-wfpv-qxp8-x5gm (ADP: CISA-ADP)

## References

- https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-wfpv-qxp8-x5gm (CNA: EEF; vendor-advisory, related)

- https://cna.erlef.org/cves/CVE-2026-65627.html (CNA: EEF; related)

- https://osv.dev/vulnerability/EEF-CVE-2026-65627 (CNA: EEF; related)

- https://github.com/potatosalad/erlang-jose/commit/a7746ecd4950f85a393136e449a91dac62b5c429 (CNA: EEF; related)

- https://github.com/potatosalad/erlang-jose/commit/857eb8e7f2d33e2c9ca2189e77226561cacaf2ad (CNA: EEF; patch)

- https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-wfpv-qxp8-x5gm (ADP: CISA-ADP; exploit)

- https://cna.erlef.org/cves/CVE-2026-65627.html (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://github.com/potatosalad/erlang-jose/commit/857eb8e7f2d33e2c9ca2189e77226561cacaf2ad (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://github.com/potatosalad/erlang-jose/commit/a7746ecd4950f85a393136e449a91dac62b5c429 (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-wfpv-qxp8-x5gm (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://osv.dev/vulnerability/EEF-CVE-2026-65627 (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-wfpv-qxp8-x5gm (134c704f-9b21-4f2e-91b3-4a467353bcc0)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-65627; retrieved 2026-11-02; source updated 2026-11-02

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-65627; retrieved 2026-11-03; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-65627; retrieved 2026-11-02; source updated Not reported

Revision: f80c133d34ff92dae13619529998d4751ad75427c5cd36b5d14de1880c7ea7cc

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