CVE-2026-15534
Description
A flaw was found in Perl. An integer overflow vulnerability in the regular expression engine's superlinear cache calculation can lead to out-of-bounds memory reads and writes. A remote attacker could exploit this by providing a specially crafted, large input string during regular expression matching. This could result in a denial of service (DoS) due to a process crash or potentially lead to heap memory corruption, enabling arbitrary code execution.
Statement
This flaw has a Moderate impact. Perl's regular expression engine contains a signed 32-bit integer overflow in the superlinear-cache size calculation (S_regmatch) that can cause out-of-bounds heap reads and writes during regex matching. Triggering it requires an application to match an attacker-controlled subject of roughly 273 MiB against a pattern containing at least 15 participating WHILEM nodes, so attack complexity is high. Successful exploitation most likely results in a process crash (denial of service); the out-of-bounds access is bit-granular into a cache bitmap, so controlled memory corruption or arbitrary code execution has not been demonstrated. Given the large, unusual inputs required and the limited reachability of the vulnerable path, Red Hat has deferred fixing this issue; residual risk is limited to a potential denial of service in applications matching very large untrusted inputs against complex patterns.
Mitigation
Applications can reduce exposure by limiting the size of untrusted input passed to regular-expression matching (the overflow requires a subject on the order of 273 MiB) and by avoiding matching untrusted data against highly complex patterns.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.7 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | Low | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Memory); DoS: Instability
This weakness can generally lead to undefined behavior and therefore crashes. When the calculated result is used for resource allocation, this weakness can cause too many (or too few) resources to be allocated, possibly enabling crashes if the product requests more resources than can be provided.
Integrity
Technical Impact: Modify Memory
If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the overflow/wraparound results in other conditions such as buffer overflows, further memory corruption may occur.
Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism
This weakness can sometimes trigger buffer overflows, which can be used to execute arbitrary code. This is usually outside the scope of the product's implicit security policy.
Availability,Other
Technical Impact: Alter Execution Logic; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
If the overflow/wraparound occurs in a loop index variable, this could cause the loop to terminate at the wrong time - too early, too late, or not at all (i.e., infinite loops). With too many iterations, some loops could consume too many resources such as memory, file handles, etc., possibly leading to a crash or other DoS.
Access Control
Technical Impact: Bypass Protection Mechanism
If integer values are used in security-critical decisions, such as calculating quotas or allocation limits, integer overflows can be used to cause an incorrect security decision.
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