- 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.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- 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? →
- 16/100 · provisional
- 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 hickory-proto package can be made to reserve large amounts of memory when it decodes a DNS message whose header claims a very large number of records, so an attacker can cause a denial of service. An attacker can send a small packet claiming up to 65,535 records, and repeated packets can exhaust memory in any code that decodes untrusted DNS messages, including servers, clients, and resolvers.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
When a DNS message is decoded, the vectors for the question, answer, authority and additional sections were created with Vec::with_capacity set to the counts in the message header. Those counts come from the sender and are not checked against the size of the message, so a single small packet that claims 65,535 records makes the decoder reserve memory for that many records (about 18 MB, according to the upstream advisory) before it reads any record and fails.
Any code that decodes untrusted DNS messages is exposed. That includes servers, and clients and resolvers that receive spoofed responses. Repeated packets can drive memory use up and cause a denial of service.
The fix caps the initial capacity at 8 entries and lets the vectors grow as records are actually decoded. It is in 0.26.2.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. No advisory context yet
- Reach16/20hickory-proto: 2.6M downloads a week
- Severity?/10Unknown. No CVSS score or vendor rating
- 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 38 if advisories confirm default setups are exposed
Impact
- Widely used
hickory-proto has 2.6m weekly downloads.Source: crates.io
What to do
Upgrade to a fixed version: 0.26.2.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by RUSTSEC-2026-0491 (Memory amplification from record counts in the DNS message header), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for RUSTSEC-2026-0491 (entry last updated 2026-11-11):
Affected:
- crates.io package hickory-proto: from 0.18.0, fixed in 0.26.2
Fixed versions: 0.26.2.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: RUSTSEC-2026-0491 is not listed as of cve.now's last read.
This KEV status is for RUSTSEC-2026-0491 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Packages (crates.io): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://rustsec.org/advisories/RUSTSEC-2026-0491.html
- https://crates.io/crates/hickory-proto
- https://github.com/hickory-dns/hickory-dns/commit/280c0e5c4e3002d73ba0762835ef82272d1d33a6
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/RUSTSEC-2026-0491
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "RUSTSEC-2026-0491"}.Timeline
- Advisory published69 days
- Record last updated
Affected versions
- hickory-protocrates.io
From 0.18.0 · fixed in 0.26.2
Fixed in 0.26.2 (released Sep 3, 2026, the day of disclosure).
The latest release, 0.26.3, is not affected.
Evidence 3
Other links · 3
- Advisory
- Repository
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about RUSTSEC-2026-0491
Is RUSTSEC-2026-0491 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
Which versions are affected by RUSTSEC-2026-0491?
hickory-proto (crates.io): from 0.18.0 before 0.26.2.Source: cve.now feed data
How do I fix RUSTSEC-2026-0491?
Upgrade to a fixed version: 0.26.2.Source: cve.now feed data