CVE-2026-125040
Description
A flaw was found in the SRT and WebVTT subtitle parser in GStreamer's gst-plugins-base. While sanitizing inline subtitle markup, the parser repeatedly searches the remaining text with unanchored regular expressions. A crafted subtitle cue with a long line of unmatched markup-like text can force quadratic CPU use and make a GStreamer-based application unresponsive.
Statement
Static review of gst-plugins-base 1.28.1 confirmed the quadratic parsing path in subrip_fix_up_markup(). Upstream states that 1.28.2 fixes the issue; the fixed source and runtime behavior were not checked in this verification. Red Hat product exposure remains unassessed.
Mitigation
Update gst-plugins-base to version 1.28.2 or later. Where updating is not yet possible, applications that do not require untrusted SRT/WebVTT subtitles can prevent automatic selection of the subparse element (for example, by setting GST_PLUGIN_FEATURE_RANK=subparse:NONE).
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 | 6.5 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | Required | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
Static Sonnet verification of gst-plugins-base 1.28.1: AV:N because crafted subtitle tracks can be delivered within network media streams to subparse; AV:L remains appropriate for deployments limited to manually opened local subtitle files. AC:L: one crafted long cue deterministically triggers quadratic regex scanning. PR:N: no account required. UI:R: the victim must play or open the media. S:U: CPU exhaustion remains in the parsing process. C:N and I:N: no disclosure or modification mechanism found. A:H: the unbounded scan can leave the application unresponsive. No dynamic timing test was run.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU)
Attackers can create crafted inputs that intentionally cause the regular expression to use excessive backtracking in a way that causes the CPU consumption to spike.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
