CyberSecBulletin
CVE-2025-62495NVD status: Analyzed

QuickJS: Integer Underflow (Wrap or Wraparound)

Published Updated By the CyberSecBulletin desk

CVE-2025-62495 is a high-severity integer underflow (wrap or wraparound) vulnerability in QuickJS, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists version 2025-09-13 as the first without the flaw, so updating QuickJS to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.47% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update QuickJS to 2025-09-13 or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
QuickJSQuickJS2025-04-26 up to, but not including, 2025-09-132025-09-13

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
AdjacentThe attacker must be on the same local network segment.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.07.1HighCNA (google.com)
CVSS 3.18.8HighNVD

Official description

An integer overflow vulnerability exists in the QuickJS regular expression engine (libregexp) due to an inconsistent representation of the bytecode buffer size. * The regular expression bytecode is stored in a DynBuf structure, which correctly uses a $\text{size}\_\text{t}$ (an unsigned type, typically 64-bit) for its size member. * However, several functions, such as re_emit_op_u32 and other internal parsing routines, incorrectly cast or store this DynBuf $\text{size}\_\text{t}$ value into a signed int (typically 32-bit). * When a large or complex regular expression (such as those generated by a recursive pattern in a Proof-of-Concept) causes the bytecode size to exceed $2^{31}$ bytes (the maximum positive value for a signed 32-bit integer), the size value wraps around, resulting in a negative integer when stored in the int variable (Integer Overflow). * This negative value is subsequently used in offset calculations. For example, within functions like re_parse_disjunction, the negative size is used to compute an offset (pos) for patching a jump instruction. * This negative offset is then incorrectly added to the buffer pointer (s->byte\_code.buf + pos), leading to an out-of-bounds write on the first line of the snippet below: put_u32(s->byte_code.buf + pos, len);

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Integer Underflow (Wrap or Wraparound)

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

More Integer Underflow (Wrap or Wraparound) vulnerabilities (CWE-191)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Technical write-ups (may include proof of concept)

Other vulnerabilities in QuickJS

All QuickJS vulnerabilities

Recent Integer Underflow (Wrap or Wraparound) vulnerabilities

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