7.5

CVE-2026-40394: varnish-software varnish_cache

CVSS: 7.5v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-40394DEBIAN-CVE-2026-40394
Published 12-04-2026Last modified 13-04-2026
Open JSON

Vulnerability summary

CVE-2026-40394 is a high (CVSS 7.5) vulnerability in varnish-software varnish_cache. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 33.3% of scored vulnerabilities.

Overall risk
30/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
0.40%
0%100%
Low · +0.17 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 12-04-2026
    PublishedVulnerability first disclosed.
  2. 13-04-2026
    Last modifiedVulnerability information updated.

Description

Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allows a "workspace overflow" denial of service (daemon panic) for certain amounts of prefetched data. The setup of an HTTP/2 session starts with a speculative HTTP/1 transport, and upon upgrading to h2 the HTTP/1 request is repurposed as stream zero. During the upgrade, a buffer allocation is made to reserve space to send frames to the client. This allocation would split the original workspace, and depending on the amount of prefetched data, the next fetch could perform a pipelining operation that would run out of workspace.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.40%

Chance of exploitation in the next 30 days

Percentile

33%

Versus all other CVEs

30-day change

+0.17 pp

From 0.24% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.40%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Varnish-software2 products
  • varnish_cache≥ 9.0.0, < 9.0.1
  • varnish_enterprise≤ 6.0.15 | 6.0.16:r1 | 6.0.16:r10 | 6.0.16:r2 | 6.0.16:r3 | 6.0.16:r4 | 6.0.16:r5 | 6.0.16:r6 | 6.0.16:r7 | 6.0.16:r8 | 6.0.16:r9
Debian1 product
  • varnishAll versions (No fix recorded)
Ubuntu1 product
  • varnishAll versions (No fix recorded)
Vinyl-cache1 product

4 vendors · 5 products

References

4 links