CVE-2026-119284: joserfc · Compact JWS size guard allocates attacker-controlled segments before rejection
Affects mcpmSource GCVE Database
Not known to be exploited · CVSS 6.9 Medium : upgrade to 2.15.0_5 when convenient.
Data as of 31 Oct 2026, 16:07 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 4.0 | 6.9 |
|---|
- Patch
- Available – fixed in 2.15.0_5
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 29 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade mcpm to 2.15.0_5.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewmcpmpkg:brew/mcpmOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available in joserfc version 2.15.0_5 that fixes this issue by validating the input size before splitting and allocating memory. Users should upgrade to version 2.15.0_5 or later to remediate this vulnerability. No additional mitigation is required beyond applying the official fix.
Description
joserfc version range >=2.14.0_4 <2.15.0_5 has a vulnerability where the compact JWS size guard allocates attacker-controlled segments before rejecting them, causing unnecessary memory allocation. This occurs because the library calls bytes.split() on the input before validating its size, leading to a copy of the payload being made even if it will be rejected. The issue is fixed in version 2.15.0_5.
References
- github.com/authlib/joserfc/security/advisories/GHSA-9pg5-8c7x-5hfx (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-119284 (opens in a new tab)
- github.com/authlib/joserfc/commit/397e04f4bbce0b94d86e31c1c003f4640af8fb39 (opens in a new tab)
- github.com/authlib/joserfc (opens in a new tab)
- github.com/authlib/joserfc/releases/tag/1.7.6 (opens in a new tab)