CVE-2026-21876

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

• ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
• AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

17.88% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 97.0% of scored records. A rank, not a probability.

NVD base score

5.3 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Modified. NVD last modified this record on 2026-06-17.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-01-08 13:55Z9 MO AGO

Last updated

2026-04-09 15:41Z6 MO AGO

Reserved

2026-01-05

Assigning CNA

GitHub_M

Record state

PUBLISHED

Severity

Critical (CVSS 9.3)

CNA CVSS vector

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

Weaknesses

• CWE-794Incomplete Filtering of Multiple Instances of Special ElementsVariant

Data version

5.2

Document digest

49a6541abc2c308f1afd77c19890e8f7f3b1f580c5db552dcf8a192faf7ced6d

• github.comhttps://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5x_refsource_CONFIRM
• github.comhttps://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83x_refsource_MISC
• github.comhttps://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6x_refsource_MISC
• github.comhttps://github.com/coreruleset/coreruleset/releases/tag/v3.3.8x_refsource_MISC
• github.comhttps://github.com/coreruleset/coreruleset/releases/tag/v4.22.0x_refsource_MISC
• github.comhttps://github.com/daytriftnewgen/CVE-2026-21876exploit