8.3

CVE-2026-56434: f5 nginx gateway fabric Use After Free

CVSS: 8.3v4.0HighAnalyzed
AliasesALPINE-CVE-2026-56434UBUNTU-CVE-2026-56434DEBIAN-CVE-2026-56434
Published 15-07-2026Last modified 15-07-2026
Open JSON

Vulnerability summary

CVE-2026-56434 is a high (CVSS 8.3) Use After Free vulnerability in f5 nginx gateway fabric. EPSS estimates a 0.42% chance of exploitation in the next 30 days, higher than 34.8% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.3/10
010
High · v4.0 (CVE.org)
EPSS score
0.42%
0%100%
Low · -0.03 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 8 · Related 3
MGASA-2026-0301OPENSUSE-SU-2026:11295-1RHSA-2026:46012RHSA-2026:59216RHSA-2026:59220RHSA-2026:59362

Timeline

  1. 15-07-2026
    PublishedVulnerability first disclosed.
  2. 15-07-2026
    Last modifiedVulnerability information updated.

Description

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuration, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to cause a use-after-free in the NGINX worker process. This issue may lead to limited modification of memory or a restart of the NGINX worker process. Impact: This vulnerability may allow remote attackers to have limited control to modify memory contents or restart the NGINX worker process. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CVSS metrics

10 scores · 7 sources · 2 versions

EPSS trend

Probability

0.42%

Chance of exploitation in the next 30 days

Percentile

35%

Versus all other CVEs

30-day change

-0.03 pp

From 0.45% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.42%

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

F55 products
  • nginx gateway fabric≥ 1.3.0, ≤ 1.6.2 | ≥ 2.0.0, < 2.6.7
  • nginx ingress controller≥ 3.5.0, ≤ 3.7.2 | ≥ 5.0.0, < 5.5.3 | ≥ 2026-lts-r1, < 2026-lts-r4 | 4.0.0 | 4.0.1
  • nginx open source≥ 1.31.2, < 1.31.3 | ≥ 0.8.11, < 1.30.4
  • nginx plus≥ R36, < R36 P7 | ≥ R33 (No fix recorded) | ≥ 37.0.0.1, < 37.0.3.1 | ≥ r33, < r36 | r36 | r36:p1 | r36:p2 | r36:p3 | r36:p4 | r36:p5 | r36:p6
  • waf≥ 4.11.0, ≤ 4.16.0 | ≥ 5.2.0, ≤ 5.8.0 | ≥ 5.9.0, < 5.13.4
Chainguard4 products
  • commercial-nginx-plus< 37.0.3.1-r0
  • nginx-mainline< 1.31.3-r0
  • nginx-stable< 1.30.4-r0
  • nginx-stable-package-config< 1.30.4-r5
Wolfi3 products
  • nginx-mainline< 1.31.3-r0
  • nginx-stable< 1.30.4-r0
  • nginx-stable-package-config< 1.30.4-r5
Alpine1 product
  • nginx< 1.26.3-r2 | < 1.28.3-r6 | < 1.30.4-r0
Debian1 product
  • nginx< 1.22.1-9+deb12u10 | < 1.26.3-3+deb13u8 | < 1.30.1-7
Ubuntu1 product
  • nginxAll versions (No fix recorded) | < 1.18.0-6ubuntu14.17 | < 1.24.0-2ubuntu7.14 | < 1.28.3-2ubuntu1.7

6 vendors · 15 products

References

7 links