CVE-2022-23901: A stack overflow re2c 2.2 exists due to infinite recursion issues in src/dfa/dead_rules.cc.

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2022-23901 is a critical-severity flaw (CVSS 9.8) affecting re2c. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A stack overflow re2c 2.2 exists due to infinite recursion issues in src/dfa/dead_rules.cc.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.6% (top 24%)
CISA exploited list	No
Weakness	CWE-787
Published	2022-03-29
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: re2c

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-03-29 12:15 UTCPublished CVE record published
2026-06-17 04:30 UTCUpdated Record last modified

re2c re2c DOWNGRADE

Affected: 2.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.2

1. Check installed version

apt-cache policy re2c || rpm -q re2c || re2c --version

2. No fixed release: DOWNGRADE to a release before 2.2 (Debian / Ubuntu)

apt-cache madison re2c sudo apt install re2c=<VERSION_BEFORE_2.2> sudo apt-mark hold re2c

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list re2c sudo dnf downgrade re2c-<VERSION_BEFORE_2.2> sudo dnf versionlock add re2c

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2022-23901?

re2c: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2022-23901 being exploited?

CVE-2022-23901 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2022-23901 affect?

CVE-2022-23901 affects re2c. Severity is critical (CVSS 9.8). A stack overflow re2c 2.2 exists due to infinite recursion issues in src/dfa/dead_rules.cc.

How urgent is CVE-2022-23901?

Priority 63/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-11958 HIGH 7.8 DOWNGRADE MITIGATE re2c 1.3 has a heap-based buffer overflow in Scanner::fill in parse/scanner.cc via a long lexeme.
CVE-2018-21232 MEDIUM 5.5 UPGRADE re2c before 2.0 has uncontrolled recursion that causes stack consumption in find_fixed_tags.

References

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