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NULL pointer dereference DoS in JavaScript::Minifier::XS minify()

IdentifiersCVE-2026-56017CWE-476

CVE-2026-56017 is a denial-of-service vulnerability in JavaScript::Minifier::XS for Perl affecting versions before 0.16. The flaw is in the regexp-versus-division disambiguation logic in JsTokenizeString within XS.xs. When the first meaningful token in the JavaScript input is a slash, and only whitespace or comments precede it, the tokenizer attempts to inspect a previous token that does not exist. The backward walk over whitespace/comment nodes can run past the head of the token list to NULL, after which the code performs a byte lookup through a NULL contents pointer using an underflowed length index. A subsequent identifier check dereferences the same NULL pointer. The bug is reachable via the public minify() API, and even input as small as a single slash byte can crash the calling Perl process.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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Successful exploitation causes the calling Perl process to crash, typically as a segmentation fault, resulting in denial of service. In deployments where a service minifies untrusted or third-party JavaScript, a remote attacker can trigger the crash by submitting crafted input, potentially causing repeated service interruption. The provided content does not establish code execution; the documented impact is process termination and service unavailability.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, avoid passing untrusted or third-party JavaScript into JavaScript::Minifier::XS minify(). As a temporary defensive measure, pre-validate or reject inputs whose first meaningful token is a slash, including cases where only whitespace or comments precede that slash. Isolating the minification function in a separate process can also reduce service-wide impact from crashes, but the primary fix is upgrading to 0.16 or later.

Remediation

Patch, then assume compromise.

Upgrade JavaScript::Minifier::XS to version 0.16 or later. Version 0.16 is specifically identified as fixing CVE-2026-56017.
PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

7 SOURCESView more in app
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Social activity6

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EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-56017
NVD
nvd.nist.gov/vuln/detail/CVE-2026-56017
MITRE CWE · CWE-476
cwe.mitre.org