Rust's regex crate vulnerable to regular expression denial of serviceGHSA-m5pq-gvj9-9vr8
HIGHFix: rust-lang/regex@ae70b41GHSA-m5pq-gvj9-9vr8 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in regex. EPSS puts its 30-day exploitation probability at 14.5% (97th percentile). A fix is available for regex — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-m5pq-gvj9-9vr8.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-m5pq-gvj9-9vr8 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
regexReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
This is a cross-post of the official security advisory. The official advisory contains a signed version with our PGP key, as well.
The Rust Security Response WG was notified that the regex crate did not properly limit the complexity of the regular expressions (regex) it parses. An attacker could use this security issue to perform a denial of service, by sending a specially crafted regex to a service accepting untrusted regexes. No known vulnerability is present when parsing untrusted input with trusted regexes.
This issue has been assigned CVE-2022-24713. The severity of this vulnerability is "high" when the regex crate is used to parse untrusted regexes. Other uses of the regex crate are not affected by this vulnerability.
Overview
The regex crate features built-in mitigations to prevent denial of service attacks caused by untrusted regexes, or untrusted input matched by trusted regexes. Those (tunable) mitigations already provide sane defaults to prevent attacks. This guarantee is documented and it's considered part of the crate's API.
Unfortunately a bug was discovered in the mitigations designed to prevent untrusted regexes to take an arbitrary amount of time during parsing, and it's possible to craft regexes that bypass such mitigations. This makes it possible to perform denial of service attacks by sending specially crafted regexes to services accepting user-controlled, untrusted regexes.
Affected versions
All versions of the regex crate before or equal to 1.5.4 are affected by this issue. The fix is include starting from regex 1.5.5.
Mitigations
We recommend everyone accepting user-controlled regexes to upgrade immediately to the latest version of the regex crate.
Unfortunately there is no fixed set of problematic regexes, as there are practically infinite regexes that could be crafted to exploit this vulnerability. Because of this, we do not recommend denying known problematic regexes.
Acknowledgements
We want to thank Addison Crump for responsibly disclosing this to us according to the Rust security policy, and for helping review the fix.
We also want to thank Andrew Gallant for developing the fix, and Pietro Albini for coordinating the disclosure and writing this advisory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | regex | all versions | 1.5.5cargo update -p regex --precise 1.5.5 |
Affected Products
debian linuxdebianfedorafedoraprojectregexrust-langDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for regex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update regex to 1.5.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m5pq-gvj9-9vr8 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 7 | firefox-0:91.8.0-1.el7_9 | RHSA-2022:1284 |
| Red Hat Enterprise Linux 7 | thunderbird-0:91.8.0-1.el7_9 | RHSA-2022:1302 |
| Red Hat Enterprise Linux 8 | firefox-0:91.8.0-1.el8_5 | RHSA-2022:1287 |
| Red Hat Enterprise Linux 8 | thunderbird-0:91.8.0-1.el8_5 | RHSA-2022:1301 |
| Red Hat Enterprise Linux 8.1 Update Services for SAP Solutions | firefox-0:91.8.0-1.el8_1 | RHSA-2022:1283 |
| Red Hat Enterprise Linux 8.1 Update Services for SAP Solutions | thunderbird-0:91.8.0-1.el8_1 | RHSA-2022:1303 |
| Red Hat Enterprise Linux 8.2 Extended Update Support | firefox-0:91.8.0-1.el8_2 | RHSA-2022:1286 |
| Red Hat Enterprise Linux 8.2 Extended Update Support | thunderbird-0:91.8.0-1.el8_2 | RHSA-2022:1326 |
Frequently Asked Questions
Is GHSA-m5pq-gvj9-9vr8 in your dependencies?
Find it across crates.io, including transitive dependencies.