CVE-2026-33170
published 2026-03-24CVE-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…
PriorityP429medium6.1CVSS 3.1
AVNACLPRNUIRSCCLILAN
EPSS
0.33%
25.2th percentile
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.
Affected
10 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | rails | — | — |
| rails | activesupport | < 7.2.3.1 | 7.2.3.1 |
| rails | activesupport | — | — |
| rails | activesupport | — | — |
| rails | activesupport | >= 0 < 7.2.3.1 | 7.2.3.1 |
| rails | activesupport | >= 8.0.0.beta1 < 8.0.4.1 | 8.0.4.1 |
| rails | activesupport | >= 8.1.0.beta1 < 8.1.2.1 | 8.1.2.1 |
| rubyonrails | rails | < 7.2.3.1 | 7.2.3.1 |
| rubyonrails | rails | >= 8.0.0 < 8.0.4.1 | 8.0.4.1 |
| rubyonrails | rails | >= 8.1.0 < 8.1.2.1 | 8.1.2.1 |
CVSS provenance
nvdv3.16.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
nvdv4.05.3MEDIUMCVSS: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
osv5.3MEDIUM
vendor_debian5.3MEDIUM
vendor_redhat5.3MEDIUM
Stop checking back — get the weekly exploitation signal.
Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
Red Hat
Rails: Active Support: Active Support: Cross-Site Scripting (XSS) due to improper HTML safety flag propagation in SafeBuffer#%
vendor_redhat·2026-03-23·CVSS 5.3
CVE-2026-33170 [MEDIUM] CWE-79 Rails: Active Support: Active Support: Cross-Site Scripting (XSS) due to improper HTML safety flag propagation in SafeBuffer#%
Rails: Active Support: Active Support: Cross-Site Scripting (XSS) due to improper HTML safety flag propagation in SafeBuffer#%
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.
A flaw was found in Active Support, a toolkit of support libraries for the Rails framework. When a `SafeBuffer` is modified in place and subsequent
Debian
CVE-2026-33170: rails - Active Support is a toolkit of support libraries and Ruby core extensions extrac...
vendor_debian·2026·CVSS 5.3
CVE-2026-33170 [MEDIUM] CVE-2026-33170: rails - Active Support is a toolkit of support libraries and Ruby core extensions extrac...
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.
Scope: local
bookworm: open
bullseye: open
forky: open
sid: open
trixie: open
OSV
CVE-2026-33170: Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework
osv·2026-03-24·CVSS 5.3
CVE-2026-33170 [MEDIUM] CVE-2026-33170: Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework
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.
OSV
Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
osv·2026-03-23
CVE-2026-33170 [MEDIUM] Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
### Impact
`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.
### Releases
The fixed releases are available at the normal locations.
### Credit
This issue was responsibly reported by @ch4n3-yoon
GHSA
Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
ghsa·2026-03-23
CVE-2026-33170 [MEDIUM] CWE-79 Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
### Impact
`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.
### Releases
The fixed releases are available at the normal locations.
### Credit
This issue was responsibly reported by @ch4n3-yoon
No detection rules found.
No public exploits indexed.
https://github.com/rails/rails/commit/50d732af3b7c8aaf63cbcca0becbc00279b215b7https://github.com/rails/rails/commit/6e8a81108001d58043de9e54a06fca58962fc2dbhttps://github.com/rails/rails/commit/c1ad0e8e1972032f3395853a5e99cea035035bebhttps://github.com/rails/rails/releases/tag/v7.2.3.1https://github.com/rails/rails/releases/tag/v8.0.4.1https://github.com/rails/rails/releases/tag/v8.1.2.1https://github.com/rails/rails/security/advisories/GHSA-89vf-4333-qx8v
2026-03-24
Published