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No exploitation reportedFix available

CVE-2026-33170

No exploitation reported by the sources we read.

  • Published2026-03-24
  • Fixed in8.1.2.1 · 8.0.4.1 · 7.2.3.1
  • WeaknessCWE-79

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, `SafeBuffer#%` does not propagate the `@html_unsafe` flag to the newly created buffer. If a `SafeBuffer` is mutated in place (e.g. via `gsub!`) and then formatted with `%` using untrusted arguments, the result incorrectly reports `html_safe? == true`, bypassing ERB auto-escaping and possibly leading to XSS. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.

Timeline

dates in UTC
  1. 2026-03-2400:16CVE publishedNVD

Versions per branch

NVD · OSV
Ruby on Rails
BranchAffectedFixed in
8.1≥ 8.1.0, < 8.1.2.18.1.2.1
8.1≥ 8.1.0.beta1, < 8.1.2.18.1.2.1
8.0≥ 8.0.0, < 8.0.4.18.0.4.1
8.0≥ 8.0.0.beta1, < 8.0.4.18.0.4.1
7.2< 7.2.3.17.2.3.1

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • rails activesupport
    Affected
    • = >= 8.1.0.beta1, < 8.1.2.1no fix stated
    • = >= 8.0.0.beta1, < 8.0.4.1no fix stated
    • = < 7.2.3.1no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-03-23

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • cinc-auditorWolfiall versions · fixed in 7.0.107-r1
  • cinc-auditorChainguardall versions · fixed in 7.0.107-r1
  • gitlab-rails-ce-18.1Chainguardall versions · no fixed version listedand 12 other packages
  • gitlab-rails-ce-18.10Chainguardall versions · fixed in 18.10.3-r1
  • gitlab-rails-ce-18.8Chainguardall versions · fixed in 18.8.11-r4
  • gitlab-rails-ce-18.9Chainguardall versions · fixed in 18.9.5-r0and 1 other package
  • gitlab-rails-ce-fips-18.10Chainguardall versions · fixed in 18.10.3-r0
  • kube-fluentd-operatorWolfiall versions · fixed in 1.18.2-r60

18 more package ranges on OSV.dev

Full record on NVD

Fix

  1. Update Ruby on Rails to 8.1.2.1 · 8.0.4.1 · 7.2.3.1

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionnone2026-03-25
  • CNACVSS 4.05.3known since 2026-10-23
  • NVDCVSS 3.16.1read 2026-10-23
  • CNAweakness (CWE)CWE-79known since 2026-10-23
  • FIRST EPSSEPSS score0.3 %2026-11-09
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryMODERATE2026-03-23

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS 4.0 vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/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
Published
2026-03-24
Last Modified
2026-06-17
NVD status
Analyzed
GitHub Advisory
GHSA-89vf-4333-qx8v

Frequently asked questions

What is CVE-2026-33170?

Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, `SafeBuffer#%` does not propagate the `@html_unsafe` flag to the newly created buffer. If a `SafeBuffer` is mutated in place (e.g. via `gsub!`) and then formatted with `%` using untrusted arguments, the result incorrectly reports `html_safe? == true`, bypassing ERB auto-escaping and possibly leading to XSS. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.

Is CVE-2026-33170 actively exploited?

Active exploitation of CVE-2026-33170 has not been confirmed. Its EPSS score was 0.3% on 2026-11-09, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-33170?

CVE-2026-33170 has a CVSS v3 base score of 6.1 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

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