Process crash via over-read in decode_tag_internal
Published Aug 20, 2026 · Updated Aug 20, 2026
Out-of-bounds read in Libevent before 2.1.13 and 2.2.2-alpha allows remote attackers to crash a process via malformed tagged RPC data. In event_tagging.c, decode_tag_internal() asks evbuffer_pullup() for at most five contiguous bytes but loops on the evbuffer's full logical length, so a fragmented six-byte tag can advance past the pulled-up window and read out of bounds. Reachability depends on software that decodes attacker-controlled evtag or evrpc messages; the published advisory confirms a crash path and does not claim memory disclosure or code execution.
Summary
What happened
Out-of-bounds read in Libevent before 2.1.13 and 2.2.2-alpha allows remote attackers to crash a process via malformed tagged RPC data. In event_tagging.c, decode_tag_internal() asks evbuffer_pullup() for at most five contiguous bytes but loops on the evbuffer's full logical length, so a fragmented six-byte tag can advance past the pulled-up window and read out of bounds. Reachability depends on software that decodes attacker-controlled evtag or evrpc messages; the published advisory confirms a crash path and does not claim memory disclosure or code execution.
The record
- CVE
- CVE-2026-63383
- Published
- Aug 20, 2026
- Updated
- Aug 20, 2026
- Vendor
- Libevent
- Product
- Libevent
- Classifications
- CWE-125, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 20, 2026CVE publishedPublication date reported by the CVE source.
- Aug 20, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.1.13
- Affected versionversion=>= 2.2.0-alpha, < 2.2.2-alpha
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- evtag_header_harness PoCproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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