CVE-2026-78384: Apache CXF: Unbounded DEFLATE Decompression in CXF JOSE/JWE and SAML Processing (Decompression Bomb)

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-09 · updated 2026-10-20
Weakness: CWE-409

Description

CompressionUtils.inflate() decompressed attacker-controlled DEFLATE data with no output-size cap. A small (~KB) crafted payload could expand to gigabytes on the heap. Reachable via JWE decryption when zip=DEF (e.g. JoseSessionTokenProvider with RSA-OAEP key wrap) and via SAML redirect/POST binding token inflation — in both cases decompression happens before/independent of trust validation. Fix: Added a configurable maximum inflated-size cap (default 10 MiB, org.apache.cxf.compression-max-inflated-size system property) to CompressionUtils.inflate(); aborts with DataFormatException once exceeded. Users are recommended to upgrade to versions 4.2.4 or 4.1.9 or 3.6.13, which fix this issue.

Affected products

Apache Software Foundation Apache CXF: before 3.6.13; from 4.0.0 before 4.1.9; from 4.2.0 before 4.2.4 — fixed in 3.6.13, 4.1.9, 4.2.4

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache CXF 3.6.13, 4.1.9, 4.2.4. Check the vendor advisory for mitigations.

References

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