CVE-2025-6491 | NULL Pointer Dereference in PHP SOAP Extension via Large XML Namespace Prefix

Exp

In PHP versions:8.1.* before 8.1.33, 8.2.* before 8.2.29, 8.3.* before 8.3.23, 8.4.* before 8.4.10 when parsing XML data in SOAP extensions, overly large (>2Gb) XML namespace prefix may lead to null pointer dereference. This may lead to crashes and affect the availability of the target server.

Published: 2025-07-13 Last update: 2025-11-04 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-6491 is rated High Exploit Risk (64.9/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.77%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2025-6491

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2025-6491

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-09 0.25% 0.77% +0.52%
2 2026-04-08 0.18% 0.25% +0.07%
3 2026-02-06 — 0.18% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-6491

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 3.6 [email protected]

Weakness enumeration for CVE-2025-6491

OS Trackers for CVE-2025-6491

vendor priority summary link
alpine medium CVE-2025-6491: 3 source package rows (php82, php83, php84); 7 state rows across 2 repos (3.22-community, edge-community); fixed 7, open 0. https://security.alpinelinux.org/vuln/CVE-2025-6491
debian not yet assigned CVE-2025-6491 not yet assigned priority: Debian including 3 source packages (php7.4, php8.2, php8.4), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-6491
redhat medium — https://access.redhat.com/security/cve/CVE-2025-6491
suse medium CVE-2025-6491 severity moderate: SUSE including 351 source package names (apache2-mod_php7-7.4.33-150400.4.51.1, apache2-mod_php8-8.0.30-150400.4.57.1, …), 1291 product×package rows across 20 product lines (SUSE Liberty Linux 8, SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS, … (20 product lines)): Fixed 1291. https://www.suse.com/security/cve/CVE-2025-6491/
ubuntu medium CVE-2025-6491 medium priority: Ubuntu including 7 source packages (php5, php7.0, …), 46 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 30, released 10, needs-triage 5, ignored 1. https://ubuntu.com/security/CVE-2025-6491

Affected software / configurations for CVE-2025-6491

Vendor Product Version Raw CPE
php php >= 8.1.0, < 8.1.33 cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
php php >= 8.2.0, < 8.2.29 cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
php php >= 8.3.0, < 8.3.23 cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
php php >= 8.4.0, < 8.4.10 cpe:2.3:a:php:php:*:*:*:*:*:*:*:*

References for CVE-2025-6491

cvelogic Threat Intelligence