CVE-2026-119284 · GHSA-9pg5-8c7x-5hfx

joserfc: Compact JWS size guard allocates attacker-controlled segments before rejection

Risk score: 46/100
CVSS: 6.9 v4.0
Published: 29 Oct 2026

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What to know

What it is: joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.6, joserfc compact JWS deserialization calls bytes.split() before enforcing the existing aggregate segment-size limits. When attacker-controlled compact serialization bytes reach des…
Affected: joserfc (pip) < 1.7.6
Fix: Upgrade joserfc to 1.7.6 or later.
Exploitation: No known exploitation

Story map

Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

joserfc: Yellow, plan it in. joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.5, joserfc.jwe.decrypt_json() accepts a JWE General JSON Serialization recipients array without a count limit and calls decrypt_cek() for every entry. An unauthenticated attacker who…

The flaws

CVE-2026-119284: Compact JWS size guard allocates attacker-controlled segments before rejection (CVSS 6.9)
CVE-2026-119283: Unbounded JWE General JSON `recipients` Array Leads to CPU Exhaustion (DoS) via Repeated RSA Private-Key Decryption (CVSS 7.5)

The fix

Upgrade joserfc: 1.7.6 · 1.7.5 or later on your release line

Who is exposed: joserfc (pip) < 1.7.5

Where it stands

No known exploitation

Connects to

Same weakness: Denial of service (CWE-400). 301 other warnings in 30 days

Why it is Yellow

CVSS 6.9 medium
On your watchlist: PyPI

Affected packages

Package	Ecosystem	Vulnerable	Fixed in
joserfc	pip	< 1.7.6	1.7.6

References

Original description

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.6, joserfc compact JWS deserialization calls bytes.split() before enforcing the existing aggregate segment-size limits. When attacker-controlled compact serialization bytes reach deserialize_compact(), the split creates copies of the header, payload, and signature segments before ExceededSizeError rejects them, causing an additional allocation approximately proportional to the supplied token. Requests that exhaust available process memory can therefore cause an availability failure even though signature verification fails. This issue is fixed in version 1.7.6.

Last activity 30 Oct 2026. Patch Forecast updates every hour.