Hickory DNS from 0.18 before 0.26.2 Memory Amplification DoS via RR Counts
Hickory DNS versions 0.18 up to but not including 0.26.2 are affected, including client and resolver mode when spoofed responses reach it. Fixed in 0.26.2.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 0.26.2
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 0.26.2.
- Published
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 26/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The DNS wire-format message parser in hickory-proto (Hickory DNS) 0.18 before 0.26.2 preallocates record vectors sized by the untrusted ANCOUNT, NSCOUNT, and ARCOUNT header fields before reading record data. Remote attackers can send a UDP datagram, or a spoofed response to a client/resolver, with these counts set to 65535, forcing about 18MB of allocation per message.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.7/10CVSS 8.7
- No patch0/5No signal
What would change the score
- Would score about 71 if added to CISA KEV
- Would score about 66 if CISA's SSVC rates exploitation active
- Would score about 31 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 0.26.2.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- hickory-dns hickory-dns
From 0.18 · fixed in 0.26.2
Evidence 2
- Advisory
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-123570
Is CVE-2026-123570 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A single incoming message forces a large memory allocation of about 18MB before parsing fails. Repeated messages can therefore exhaust memory, causing a denial of service.Source: vulncheck.com, github.com
Which versions are affected by CVE-2026-123570?
hickory-dns: from 0.18 before 0.26.2.Source: cve.now feed data
Am I affected, and how do I check?
Affects hickory-proto and hickory-dns versions 0.18 up to but not including 0.26.2. The same code path is reachable in client/resolver mode via spoofed responses. To check, compare the hickory-proto or hickory-dns version in use against that range.Source: vulncheck.com, github.com
How do I fix CVE-2026-123570?
Upgrade hickory-proto and hickory-dns to 0.26.2 or later, which is the listed fixed version. No workaround is listed in the available facts.Source: vulncheck.com, github.com