Bug 2458516 (CVE-2026-4890) - CVE-2026-4890 dnsmasq: NSEC bitmap parsing infinite loop
Summary: CVE-2026-4890 dnsmasq: NSEC bitmap parsing infinite loop
Keywords:
Status: NEW
Alias: CVE-2026-4890
Deadline: 2026-05-09
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-14 22:39 UTC by OSIDB Bzimport
Modified: 2026-05-12 17:02 UTC (History)
3 users (show)

Fixed In Version:
Clone Of:
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Description OSIDB Bzimport 2026-04-14 22:39:35 UTC 
NSEC/NSEC3 bitmap window iteration in dnssec.c advances by p[1] instead of p[1] + 2, missing the 2-byte window header. When bitmap_length=0, neither rdlen nor p change, creating an infinite loop. Two instances at dnssec.c:1290 and dnssec.c:1450. Reachable before RRSIG validation so no valid signatures are needed. One of the two sites was coincidentally fixed in 2.92. Fix: add +2 to both the pointer advance and rdlen decrement.
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