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TI-2026-45237 Aliases CVE-2026-63495

Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames

Priority HIGH 72CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 1 fixed, 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-400.

Summary

Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws->incomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00609 49th percentileScored 2026-11-07
Fix Partial libevent (libevent): 2.2.2-alphaRed Hat: 1 advisoryRed Hat: 1 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
libeventlibevent2.2.0-alpha-dev to before 2.2.2-alpha2.2.2-alphaPatch availableCNA
  • libevent Vendorlibevent Affected 2.2.0-alpha-dev to before 2.2.2-alpha Fixed in 2.2.2-alpha Patch available CNA

Remediation

  • Fix · CNA libevent (libevent) Fixed in 2.2.2-alpha

Red Hat 1 advisory

  • RHSA-2026:41176 Released 2026-07-17 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images libevent-2.1.12-19.hum1@aarch64, libevent-2.1.12-19.hum1@src, libevent-2.1.12-19.hum1@x86_64 +4

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Will not fix
Red Hat OpenShift Container Platform 4AffectedNo fix yet
Red Hat OpenShift Container Platform 5AffectedNo fix yet
Red Hat Hardened ImagesFixed RHSA-2026:41176
Not affected: 5 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-63495
  2. 2026-10-30 Affected versions changed · Red Hat

References

Other 3

  • TI-2026-45182 libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling CVSS 4.0CRITICAL 9.2
  • TI-2026-45184 Libevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` return value. CVSS 4.0HIGH 8.7
  • TI-2026-45183 Libevent: decode_tag_internal() can lead to out-of-bounds read CVSS 4.0HIGH 8.7
  • TI-2026-45187 Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response CVSS 3.1HIGH 7.0
  • TI-2026-45180 Libevent: Null Pointer Dereference in `evws_new_session` CVSS 4.0MEDIUM 5.7
  • TI-2026-45185 Libevent: HTTP header handling bugs create risk of access control bypass. CVSS 4.0CRITICAL 9.2
See all 9 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences