Affects GitHub Enterprise Server, a widely used on-prem product; unauthenticated SSRF could expose internal data across many orgs.
CVE-2026-5921
Unauthenticated SSRF in GitHub Enterprise Server enables timing-based internal data exposure.
Is CVE-2026-5921 being exploited?
Not confirmed. CVE-2026-5921 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.42% probability of exploitation in the next 30 days.
How severe is CVE-2026-5921?
CVE-2026-5921 is rated High with a CVSS score of 8.9. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-5921?
Yes. A fix has been recorded for CVE-2026-5921. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-5921 affect?
CVE-2026-5921 affects GitHub Enterprise Server < 3.21 (pre-3.21). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-5921?
Upgrade to 3.21+ or latest patched release.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Exfiltrate internal environment vars via redirect chaining and timing analysis; unauthenticated access to internal services.
Patch when possible
- affected>= 3.14.0 and < 3.14.26
- affected>= 3.15.0 and < 3.15.21
- affected>= 3.16.0 and < 3.16.17
- affected>= 3.17.0 and < 3.17.14
- affected>= 3.18.0 and < 3.18.8
- affected>= 3.19.0 and < 3.19.5
- affected>= 3.20.0 and < 3.20.1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.