CVE-2026-77299: DoS (CVSS 7.5)

Description

Regexp2 is a feature-rich RegExp engine for Go. Prior to version 2.3.0, when regexp2 compiles and matches a pattern containing a large fixed-count quantifier applied to a zero-width subexpression — e.g. (?:){50000000} — the match engine executes the empty loop body m-1 times, pushing two integers onto the backtracking stack on every iteration. Because the parser accepts any repetition count up to math.MaxInt32 and the backtracking stack grows without bound, a pattern of fewer than 20 bytes matched against an empty input can force multi-gigabyte allocation and OOM-kill the process. MatchTimeout does not fully mitigate this because the memory is allocated faster than the 100 ms timeout clock can fire. This issue has been patched in version 2.3.0.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0035

Probability of exploitation

0.29%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

CWE-770 CWE-770

References

Other References

https://github.com/dlclark/regexp2/commit/6e446cb3a57a0f20112bc24353604fd00bdb309a https://github.com/dlclark/regexp2/releases/tag/v2.3.0 https://github.com/dlclark/regexp2/security/advisories/GHSA-wq9v-j77v-qr26 https://github.com/dlclark/regexp2/security/advisories/GHSA-wq9v-j77v-qr26

Frequently Asked Questions

What is CVE-2026-77299? +

Regexp2 is a feature-rich RegExp engine for Go. Prior to version 2.3.0, when regexp2 compiles and matches a pattern containing a large fixed-count quantifier applied to a zero-width subexpression — e.g. (?:){50000000} — the match engine executes the empty loop body m-1 times, pushing two integers onto the backtracking stack on every iteration. Because the parser accepts any repetition count up to math.MaxInt32 and the backtracking stack grows without bound, a pattern of fewer than 20 bytes matched against an empty input can force multi-gigabyte allocation and OOM-kill the process. MatchTimeout does not fully mitigate this because the memory is allocated faster than the 100 ms timeout clock can fire. This issue has been patched in version 2.3.0. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-77299? +

CVE-2026-77299 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0035, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-77299? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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