CVE-2026-42534Patch(nlnetlabs / unbound)

LOWCVSS 5.3 · MEDIUM

Signal is active with 2 mentions in latest observed window

Immediate actions

  • Patch nlnetlabs unbound systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD description

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.

0.5/ 10 priority

Sources & remediation

Weakness type (CWE)
CWE-440CWE-911

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

NONE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

  • unbound

Threat summary

  • Patch or workaround signal is available
  • 2 mentions across 1 observed day

What's happening

  • Patch or workaround mentioned in 2 signals
  • Technical details provided in 1 signal
  • 2 total mentions across 1 day

Affected systems

Vendors
Products
unbound

Deep dive

Activity timeline2 mentions / 1d
01122Mentions · 2026-05-20: 2Patch / Workaround · 2026-05-20: 2Technical Details · 2026-05-20: 105-20
Signal classification1 categories
Patch
2100.0%
Referenced assets1 URL
By indicator
Full discourse2 posts
  • Yasuhiro Morishita@OrangeMorishita
    Patch

    ・Fix CVE-2026-33278, Possible remote code execution during DNSSEC validation. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-42944, Heap overflow and crash with multiple nsid, cookie, padding EDNS options. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-42959, Crash during DNSSEC validation of malicious content. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-32792, Packet of death with DNSCrypt. Thanks to Andrew Griffiths from ‘http://calif.io’ for the report. ・Fix CVE-2026-40622, “Ghost domain name” variant. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-41292, Parsing a long list of incoming EDNS options degrades performance. Thanks to GitHub user ‘N0zoM1z0’, also Qifan Zhang from Palo Alto Networks, for the report. ・Fix CVE-2026-42534, Jostle logic bypass degrades resolution performance. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-42923, Degradation of service with unbounded NSEC3 hash calculations. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-42960, Possible cache poisoning attack while following delegation. Thanks to TaoFei Guo from Peking University, Yang Luo and JianJun Chen, Tsinghua University, for the report. ・Fix CVE-2026-44390, Unbounded name compression in certain cases causes degradation of service. Thanks to Qifan Zhang, Palo Alto Networks, for the report. ・Fix CVE-2026-44608, Use after free and crash in RPZ code. Thanks to Qifan Zhang, Palo Alto Networks, for the report.

    Post summary

    The notice lists several CVE fixes with brief technical summaries, confirming that patches are available but offering no PoC, exploit code, or evidence of active exploitation.

    11010442
    4.5K followersView on X
  • Yasuhiro Morishita@OrangeMorishita
    Patch

    "This release consolidates security fixes for issues reported over a period of time. There are fixes for CVE-2026-33278, CVE-2026-42944, CVE-2026-42959, CVE-2026-32792, CVE-2026-40622, CVE-2026-41292, CVE-2026-42534, CVE-2026-42923, CVE-2026-42960, CVE-2026-44390 and CVE-2026-44608."

    Post summary

    The text announces a release that consolidates patches for a series of CVEs, indicating that updates are available to address these vulnerabilities.

    10000228
    4.5K followersView on X
CPE platform detail1 entries

1 of 1 entries

PartVendorProductVersionTarget SWTarget HW
Appnlnetlabsunbound---

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