CVE-2026-34475: Varnish Cache · Incorrect Behavior Order: Validate Before Canonicalize
Affects Varnish CacheSource CVE Database V5
Not known to be exploited · CVSS 5.4 Medium : upgrade to 8.0.1 or 6.0.17 LTS when convenient.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 8.0.1, 6.0.17 LTS
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 27 Mar 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 Varnish Cache to 8.0.1 or 6.0.17 LTS.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| varnish-softwareVarnish Cache | Affected
| Fixed in
|
AI-suggested
Organizations should upgrade Varnish Cache to version 8.0.1 or later and Varnish Enterprise to 6.0.16r12 or later, where this vulnerability is fixed. If immediate patching is not feasible, administrators should implement strict input validation and URL normalization at the web application firewall (WAF) or reverse proxy level to ensure URLs are properly canonicalized before validation. Monitoring and logging of unusual or malformed requests targeting the root path '/' should be enhanced to detect potential exploitation attempts. Additionally, review and tighten cache key generation logic to prevent unauthorized cache entries. Employ network segmentation and access controls to limit exposure of Varnish Cache instances to untrusted networks. Regularly audit and update security policies related to caching infrastructure. Finally, stay informed about any emerging exploits or patches related to this CVE.
Description
Varnish Cache before 8.0.1 and Varnish Enterprise before 6.0.16r12, in certain unchecked req.url scenarios, mishandle URLs with a path of / for HTTP/1.1, potentially leading to cache poisoning or authentication bypass.