Expr has Denial of Service via Unbounded Recursion in Builtin Functions

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2025-68156: 0.42% estimated exploitation activity in the next 30 days; percentile 36.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Several builtin functions in Expr, including flatten, min, max, mean, and median, perform recursive traversal over user-provided data structures without enforcing a maximum recursion depth. If the evaluation environment contains deeply nested or cyclic data structures, these functions may recurse indefinitely until exceed the Go runtime stack limit. This results in a stack overflow panic, causing the host application to crash. While exploitability depends on whether an attacker can influence or inject cyclic or pathologically deep data into the evaluation environment, this behavior represents a denial-of-service (DoS) risk and affects overall library robustness. Instead of returning a recoverable evaluation error, the process may terminate unexpectedly. Impact In affected versions, evaluation of expressions that invoke certain builtin functions on untrusted or insufficiently validated data structures can lead to a process-level crash due to stack exhaustion. This issue is most…

Published by the source

16 Dec 2025, 22:34 UTC

Last modified by the source

16 Dec 2025, 22:34 UTC

Source last checked

26 Oct 2026, 15:13 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cfpf-hrx2-8rv6

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# Patch Next advisory brief: CVE-2025-68156

Advisory: Expr has Denial of Service via Unbounded Recursion in Builtin Functions
IDs: CVE-2025-68156, GHSA-cfpf-hrx2-8rv6
Record: https://patchnext.com/advisories/cve-2025-68156 (revision 1, source checked 26 Oct 2026, 15:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/expr-lang/expr 1.17.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/expr-lang/expr: affected < 1.17.7; fixed in 1.17.7

## Suggested inspection (read-only)
- Go github.com/expr-lang/expr: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/expr-lang/expr.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cfpf-hrx2-8rv6 (GitHub-reviewed advisory GHSA-cfpf-hrx2-8rv6 lists affected ranges: Go github.com/expr-lang/expr >=0 <1.17.7)

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