URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep
Noroxi assessment
Priority: Monitor (action score 26/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.22% (FIRST EPSS).
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: azl3 perl-URI 5.21-2 on Azure Linux 3.0 5.21-3; azl3 perl-URI 5.21-3 on Azure Linux 3.0 5.21-3.
Low priority for now. Upgrade to azl3 perl-URI 5.21-2 on Azure Linux 3.0 5.21-3; azl3 perl-URI 5.21-3 on Azure Linux 3.0 5.21-3 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label. Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.
- Published
- Aug 31, 2026
- Updated
- Sep 3, 2026
- EPSS
- 0.2% · 12th percentile
- CWE
- CWE-1289
Report tools
Action score
26
Monitor
Low priority for now.
- CVSS
- 26 / 40 · 6.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
Running WordPress? Scan your site free with WP Lens
Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (CPANSec). Independent of NVD's CPE analysis and usually ahead of it.
cpan.org/modules URI
- before 5.36affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | perl-URI | before 5.27-3.el10_2.1 | 5.27-3.el10_2.1 |
| AlmaLinux:8 | perl-URI | before 1.73-4.el8_10 | 1.73-4.el8_10 |
| AlmaLinux:9 | perl-URI | before 5.09-3.el9_8.1 | 5.09-3.el9_8.1 |
| Debian:12 | liburi-perl | from 0 | — |
| Debian:14 | liburi-perl | before 5.36-1 | 5.36-1 |
| openSUSE:Leap 16.0 | perl-URI | before 5.310.0-160000.3.1 | 5.310.0-160000.3.1 |
| openSUSE:Tumbleweed | perl-URI | before 5.360.0-1.1 | 5.360.0-1.1 |
| Red Hat:enterprise_linux:10.2 | perl-URI | before 0:5.27-3.el10_2.1 | 0:5.27-3.el10_2.1 |
| Red Hat:enterprise_linux:8::baseos | perl-URI | before 0:1.73-4.el8_10 | 0:1.73-4.el8_10 |
| Red Hat:enterprise_linux:9::appstream | perl-URI | before 0:5.09-3.el9_8.1 | 0:5.09-3.el9_8.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP7 | perl-URI | before 1.73-150000.3.3.1 | 1.73-150000.3.3.1 |
| SUSE:Linux Enterprise Server 16.0 | perl-URI | before 5.310.0-160000.3.1 | 5.310.0-160000.3.1 |
| SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | perl-URI | before 1.60-9.3.1 | 1.60-9.3.1 |
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| azl3 perl-URI 5.21-2 on Azure Linux 3.0 | 5.21-3 | Microsoft (MSRC) |
| azl3 perl-URI 5.21-3 on Azure Linux 3.0 | 5.21-3 · Release Notes | Microsoft (MSRC) |
| almalinux:perl-URI | 5.27-3.el10_2.1 · AlmaLinux:10 | Package registry (OSV) |
| debian:liburi-perl | 5.36-1 · Debian:14 | Package registry (OSV) |
| opensuse:perl-URI | 5.360.0-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:perl-URI | 0:5.27-3.el10_2.1 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| suse:perl-URI | 5.310.0-160000.3.1 · SUSE:Linux Enterprise Server 16.0 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-1289 · Improper Validation of Unsafe Equivalence in InputCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (4 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.