CVE-2026-109399 json
SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates
published 28d ago modified 22d ago also EUVD-2026-97496
- cvss
- 8.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 10%
- public exploits
- 0
- none known
Summary
SWUpdate through 2026.05.1 contains an improper certificate validation vulnerability in crypto/swupdate_cms_verify_openssl.c that trusts untrusted X.509 certificates embedded in CMS SignedData for chain building. Attackers holding a signing key from a sibling intermediate under the same root can embed that intermediate in the signature to install malicious updates.
Patch / fix
- swupdate Debian 12 2022.12+dfsg-4+deb12u3
- swupdate Debian 14 2026.05+dfsg-1
debian advisories DEBIAN-CVE-2026-109399
Is CVE-2026-109399 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 22d ago
Exploit prediction
0.21% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 9.2 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CNA | 4.0 | 9.2 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/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 |
Affected products
- sbabic swupdate
Classification
- Weakness
-
- CWE-295 Improper Certificate Validation
References
-
github.com
/sbabic/swupdate/commit/e66c5640664a31668926a24c0c84b6b6570dc0d9
patch
-
groups.google.com
/g/swupdate/c/dsoMcGFnEns
technical-description, mailing-list
-
github.com
/sbabic/swupdate/blob/2026.05.1/crypto/swupdate_cms_verify_openssl.c
technical-description
-
github.com
/sbabic/swupdate
product
-
vulncheck.com
/advisories/swupdate-through-2026.05.1-cms-signature-verification-bypass-via-embedded-intermediates
third-party-advisory
Sources
- CVE List CVE-2026-109399
- NVD CVE-2026-109399
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.