CVE-2021-37746: textview_uri_security_check in textview.c in Claws Mail before 3.18.0, and Sylpheed through 3.7.0, does not have sufficient link checks befo
Noroxi assessment
Priority: Monitor (action score 24/100)
- 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: 1.1% (FIRST EPSS); higher than 67.2% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
- Fixed version: claws-mail (Debian:12) 3.18.0-1; sylpheed (Debian:12) 3.8.0~beta1-1+deb12u1; sylpheed (Debian:13) 3.8.0~beta1-2+deb13u1.
Low priority for now. Upgrade to claws-mail (Debian:12) 3.18.0-1; sylpheed (Debian:12) 3.8.0~beta1-1+deb12u1; sylpheed (Debian:13) 3.8.0~beta1-2+deb13u1 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
textview_uri_security_check in textview.c in Claws Mail before 3.18.0, and Sylpheed through 3.7.0, does not have sufficient link checks before accepting a click.
- Published
- Jul 30, 2021
- Updated
- Jun 17, 2026
- EPSS
- 1.1% · 67th percentile
- CWE
- CWE-601
Report tools
Action score
24
Monitor
Low priority for now.
- CVSS
- 24 / 40 · 6.1 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.1%
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.
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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.
| Vendor | Product | CPE |
|---|---|---|
| claws-mail | claws-mail | cpe:2.3:a:claws-mail:claws-mail |
| sylpheed project | sylpheed | cpe:2.3:a:sylpheed_project:sylpheed |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- claws-mail claws-mailbefore 3.18.0
- fedoraproject fedora33
- fedoraproject fedora34
- sylpheed project sylpheedup to 3.7.0 inclusive
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | claws-mail | before 3.18.0-1 | 3.18.0-1 |
| Debian:12 | sylpheed | before 3.8.0~beta1-1+deb12u1 | 3.8.0~beta1-1+deb12u1 |
| Debian:13 | sylpheed | before 3.8.0~beta1-2+deb13u1 | 3.8.0~beta1-2+deb13u1 |
Same product
claws-mail: all recordsOther highest-scoring records for the same primary product.
- CVE-2020-15917common/session.c in Claws Mail before 3.17.6 has a protocol violation because suffix data after STARTTLS is mishandled.40Plan
- CVE-2020-16094In imap_scan_tree_recursive in Claws Mail through 3.17.6, a malicious IMAP server can trigger stack consumption because of unlimited recursi31Monitor
- CVE-2015-8614Multiple stack-based buffer overflows in the (1) conv_jistoeuc, (2) conv_euctojis, and (3) conv_sjistoeuc functions in codeconv.c in Claws M30Monitor
Published before and after this one in the same product
- ← EarlierCVE-2012-4507Oct 22, 2012 · The strchr function in procmime.c in Claws Mail (aka claws-mail) 3.8.1 allows remote attackers to cause a denial of service (NULL pointer de21Monitor
- ← EarlierCVE-2014-2576Oct 15, 2014 · plugins/rssyl/feed.c in Claws Mail before 3.10.0 disables the CURLOPT_SSL_VERIFYHOST check for CN or SAN host name fields, which makes it ea28Monitor
- ← EarlierCVE-2015-8708Apr 11, 2016 · Stack-based buffer overflow in the conv_euctojis function in codeconv.c in Claws Mail 3.13.1 allows remote attackers to have unspecified imp29Monitor
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 |
|---|---|---|
| debian:claws-mail | 3.18.0-1 · Debian:12 | Package registry (OSV) |
| debian:sylpheed | 3.8.0~beta1-1+deb12u1 · Debian:12 | 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.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
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.
- A user must open a link or visit a page.
- 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
Impact can extend beyond the vulnerable component (scope changes).
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-601 · URL Redirection to Untrusted Site ('Open Redirect')CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (4 more)Show less
- git.claws-mail.org/?p=claws.git%3Ba=commit%3Bh=ac286a71ed78429e16c612161251b9ea90ccd431
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L2QNUIWASJLPUZZKWICGCEGYJZCQE7NH/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RCJXHUSYHGVBSH2ULD7HNXLM7QNRECZ6/
- sylpheed.sraoss.jp/sylpheed/v3.7/sylpheed-3.7.0.tar.xz
Vendor advisories and official records. Exploit/PoC links are deliberately left out.