CVE-2026-42926: F5 NGINX Open Source · Encoding Error
Affects F5 NGINX Open SourceSource CVE Database V5
Not known to be exploited · CVSS 5.8 Medium : upgrade to 1.30.1 when convenient.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.30.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 13 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
Public exploit code: GitHub proofs of concept
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), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade F5 NGINX Open Source to 1.30.1.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| F5NGINX Open Source | Affected
| Fixed in
|
AI-suggested
If you cannot patch yet, users should review their proxy_http_version and proxy_set_body configurations to assess exposure. No vendor-provided mitigation or temporary fix is currently available.
Description
When NGINX Open Source is configured to proxy HTTP/2 traffic by setting proxy_http_version to 2, and also uses proxy_set_body, an attacker may be able to inject frame headers and payload bytes to the upstream peer. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.