CVE-2026-42794: Reflected XSS via backslash bypass in GraphiQL js_escape in absinthe_plug

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-08 · updated 2026-10-26
Weakness: CWE-79

Description

Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in absinthe-graphql absinthe_plug allows reflected cross-site scripting via the GraphiQL interface. 'Elixir.Absinthe.Plug.GraphiQL':js_escape/1 in lib/absinthe/plug/graphiql.ex escapes single quotes and newlines in the query GET parameter before embedding it in an inline JavaScript string, but does not escape backslashes. An attacker can bypass the escaping by prefixing a quote with a backslash (e.g. \'), breaking out of the string context and executing arbitrary JavaScript in the victim's browser. This issue affects absinthe_plug: from 1.2.0 before 1.5.10.

Affected products

absinthe-graphql absinthe_plug: from 1.2.0 before 1.5.10 — fixed in 1.5.10

How to fix

Upgrade to a fixed version: absinthe-graphql absinthe_plug 1.5.10. Check the vendor advisory for mitigations.

References

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