---
title: "CVE-2026-27614: Bugsink is vulnerable to Stored XSS via Pygments fallback in stacktrace rendering"
url: https://erroneo.us/security/cve/CVE-2026-27614/
description: "CVE-2026-27614 (bugsink (PyPI)): Bugsink is a self-hosted error tracking tool. In versions prior to 2.0.13, an unauthenticated attacker who can submit…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-25
date_modified: 2026-02-25
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-27614"
kev: false
cvss: 9.3
epss: 0.0044
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-27614: Bugsink is vulnerable to Stored XSS via Pygments fallback in stacktrace rendering

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.4% , percentile 37: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 37% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
- Only applies if your dependency tree includes bugsink (PyPI) <= 2.0.12, fixed in 2.0.13 . Check your lockfile, including transitive dependencies.

## What it is

Bugsink is a self-hosted error tracking tool. In versions prior to 2.0.13, an unauthenticated attacker who can submit events to a Bugsink project can store arbitrary JavaScript in an event. The payload executes only if a user explicitly views the affected Stacktrace in the web UI. When Pygments returns more lines than it was given (a known upstream quirk that triggers with Ruby heredoc-style input), pygmentizelines() in theme/templatetags/issues.py:75-77 falls back to returning the raw input lines. marksafe() at line 111-113 is then applied unconditionally - including to those unsanitized raw lines. Since DSN endpoints are public by Sentry protocol, no account is needed to inject. The payload sits in the database until an admin looks at the event. Successful exploitation requires that the attacker to be able to submit events to the project (i.e. knows the DSN or can access a client that uses it), the Bugsink ingest endpoint is reachable to the attacker, and an administrator explicitly views the crafted event in the UI. Under those conditions, the attacker can execute JavaScript in the administrator’s browser and act with that user’s privileges within Bugsink. Version 2.0.13 fixes the vulnerability.

## Affected packages

- PyPI `bugsink` <= 2.0.12 → fixed: 2.0.13

## Affected products (CVE record)

- bugsink bugsink: < 2.0.13

## Severity

- GitHub_M CVSS 3.1: 9.3 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.3 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.44% probability of exploitation activity in the next 30 days; percentile 37.

## Sources

- [GitHub Advisory GHSA-vp6q-7m36-pq3w](https://github.com/advisories/GHSA-vp6q-7m36-pq3w)
- [CVE.org record CVE-2026-27614](https://www.cve.org/CVERecord?id=CVE-2026-27614)
- [NVD entry CVE-2026-27614](https://nvd.nist.gov/vuln/detail/CVE-2026-27614)
- [github.com](https://github.com/bugsink/bugsink/security/advisories/GHSA-vp6q-7m36-pq3w)
- [github.com](https://github.com/bugsink/bugsink/commit/e784d6aeb0d5f29b40c2779d2544c2b9ef097ee9)
- [github.com](https://github.com/bugsink/bugsink/releases/tag/2.0.13)

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Source page: https://erroneo.us/security/cve/CVE-2026-27614/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt