Vulnerability · CVE-2025-62494
A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine.
Published Oct 16, 2025 · catalog updated Oct 16, 2025 · QuickJS QuickJS
Last checked Oct 26, 2026. A connected source was read within the last 7 days.
Check if you run it
No confirmed exploitation is on record for CVE-2025-62494. EPSS is 0.51%. Act only if a listed version of QuickJS QuickJS is installed.
Gaps on this record
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
Same product and reporting
- CVE-2025-12745 · Medium
- CVE-2025-62496 · High
- CVE-2025-62495 · High
- CVE-2025-62493 · Medium
- CVE-2025-62492 · Medium
- Severity
- High7.1
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.51%
- Remediation
- Version ranges on file
- Affected products
- vendor QuickJS QuickJS 2025-04-26 <2025-09-13
A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine. * The code first checks if the left-hand operand is a string. * It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree. This conversion can trigger a callback (e.g., toString or valueOf). * During this callback, an attacker can modify the type of the left-hand operand in memory, changing it from a string to a different type (e.g., an object or an array). * The code then proceeds to call JS_ConcatStringInPlace, which still treats the mod
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- vendor QuickJS QuickJS 2025-04-26 <2025-09-132025-04-26 <2025-09-13
How to fix CVE-2025-62494
Upgrade
CVE-2025-62494 lists a fix boundary at 2025-09-13. Compare the installed build with that boundary before you change production.
Version check
Seen in 2025-04-26 <2025-09-13
Advisory
Open the cve_org record and follow its fix.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2025-62494. EPSS is 0.51%. Act only if a listed version of QuickJS QuickJS is installed.
Which versions are affected?
Compare what you have installed with QuickJS QuickJS 2025-04-26 <2025-09-13 2025-04-26 <2025-09-13. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
No weakness class is stored. EPSS 0.51%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Oct 16, 2025 · EUVD
Detected
A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine. * The code first checks if the left-hand operand is a string. * It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree. This conversion can trigger a callback (e.g., toString or valueOf). * During this callback, an attacker can modify the t
Oct 16, 2025 · EUVD
Updated
A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine. * The code first checks if the left-hand operand is a string. * It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree. This conversion can trigger a callback (e.g., toString or valueOf). * During this callback, an attacker can modify the t
Sources
- CVE.orgVulnerability recordCVE-2025-62494
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2025-62494
30-day exploitation probability 0.51%
first.org - EUVDVulnerability recordEUVD-2025-34780
A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine. * The code first checks if the left-hand operand is a string. * It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree.
euvd.enisa.europa.eu
References
Freshness
Last verified in this catalog Oct 26, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.
- FIRST EPSSOct 26, 2026
- CVE.orgOct 26, 2026
- EUVDOct 26, 2026