CVE-2021-22947: When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using STARTTLS to upgrade to TLS security, the server
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: 3% (FIRST EPSS); higher than 87.4% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
- Fixed version: curl (Alpine:v3.11) 7.79.0-r0; curl (Debian:10) 7.64.0-4+deb10u3; curl (Debian:11) 7.74.0-1.3+deb11u2.
- Mentioned 6 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to curl (Alpine:v3.11) 7.79.0-r0; curl (Debian:10) 7.64.0-4+deb10u3; curl (Debian:11) 7.74.0-1.3+deb11u2 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
When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using STARTTLS to upgrade to TLS security, the server can respond and send back multiple responses at once that curl caches. curl would then upgrade to TLS but not flush the in-queue of cached responses but instead continue using and trustingthe responses it got *before* the TLS handshake as if they were authenticated.Using this flaw, it allows a Man-In-The-Middle attacker to first inject the fake responses, then pass-through the TLS traffic from the legitimate server and trick curl into sending data back to the user thinking the attacker's injected data comes from the TLS-protected server.
- Published
- Sep 29, 2021
- Updated
- Oct 14, 2026
- EPSS
- 3.0% · 87th percentile
- CWE
- CWE-310
Report tools
Action score
24
Monitor
Low priority for now.
- CVSS
- 23 / 40 · 5.9 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 3.0%
CISA SSVC decision
- Exploitation
- proof of concept
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 5.9
- CNA · hackerone
- 5.9
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
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.
| Vendor | Product | CPE |
|---|---|---|
| haxx | curl | cpe:2.3:a:haxx:curl |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| netapp | cloud backup | cpe:2.3:a:netapp:cloud_backup |
| netapp | clustered data ontap | cpe:2.3:a:netapp:clustered_data_ontap |
| netapp | h300s firmware | cpe:2.3:o:netapp:h300s_firmware |
| netapp | h300s | cpe:2.3:h:netapp:h300s |
| netapp | h500s firmware | cpe:2.3:o:netapp:h500s_firmware |
| netapp | h500s | cpe:2.3:h:netapp:h500s |
| netapp | h700s firmware | cpe:2.3:o:netapp:h700s_firmware |
| netapp | h700s | cpe:2.3:h:netapp:h700s |
| netapp | h300e firmware | cpe:2.3:o:netapp:h300e_firmware |
and 22 more
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- apple macosbefore 12.3
- debian debian linux10.0
- debian debian linux11.0
- debian debian linux9.0
- fedoraproject fedora33
- fedoraproject fedora35
- haxx curl7.20.0 and later · before 7.79.0
- netapp cloud backupall versions
- netapp clustered data ontapall versions
- netapp h300e firmwareall versions
- netapp h300s firmwareall versions
- netapp h410s firmwareall versions
- netapp h500e firmwareall versions
- netapp h500s firmwareall versions
- netapp h700e firmwareall versions
- netapp h700s firmwareall versions
- netapp solidfire baseboard management controller firmwareall versions
- oracle commerce guided search11.3.2
- oracle communications cloud native core binding support function1.11.0
- oracle communications cloud native core binding support function22.1.3
Versions reported by the vendor
Affected version ranges reported by the assigning authority (hackerone). Independent of NVD's CPE analysis and usually ahead of it.
n/a https://github.com/curl/curl
- curl 7.20.0 to and including 7.78.0affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.11 | curl | from 7.20.0 · before 7.79.0-r0 | 7.79.0-r0 |
| Debian:10 | curl | before 7.64.0-4+deb10u3 | 7.64.0-4+deb10u3 |
| Debian:11 | curl | before 7.74.0-1.3+deb11u2 | 7.74.0-1.3+deb11u2 |
| Debian:12 | curl | before 7.79.1-1 | 7.79.1-1 |
| Debian:9 | curl | before 7.52.1-5+deb9u16 | 7.52.1-5+deb9u16 |
| openSUSE:Leap 15.2 | curl | before 7.66.0-lp152.3.24.1 | 7.66.0-lp152.3.24.1 |
| openSUSE:Leap 15.2 | curl-mini | before 7.66.0-lp152.3.24.1 | 7.66.0-lp152.3.24.1 |
| openSUSE:Leap 15.3 | curl | before 7.66.0-4.27.1 | 7.66.0-4.27.1 |
| Red Hat:enterprise_linux:8::baseos | curl | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | curl-debuginfo | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | curl-debugsource | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | curl-minimal-debuginfo | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | libcurl | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | libcurl-debuginfo | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | libcurl-devel | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | libcurl-minimal | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:enterprise_linux:8::baseos | libcurl-minimal-debuginfo | before 0:7.61.1-18.el8_4.2 | 0:7.61.1-18.el8_4.2 |
| Red Hat:rhel_dotnet:3.1::el7 | rh-dotnet31-curl | before 0:7.61.1-22.el7_9 | 0:7.61.1-22.el7_9 |
| Red Hat:rhel_dotnet:3.1::el7 | rh-dotnet31-curl-debuginfo | before 0:7.61.1-22.el7_9 | 0:7.61.1-22.el7_9 |
| Red Hat:rhel_dotnet:3.1::el7 | rh-dotnet31-libcurl | before 0:7.61.1-22.el7_9 | 0:7.61.1-22.el7_9 |
| Red Hat:rhel_dotnet:3.1::el7 | rh-dotnet31-libcurl-devel | before 0:7.61.1-22.el7_9 | 0:7.61.1-22.el7_9 |
| Red Hat:rhel_eus:8.2::baseos | curl | before 0:7.61.1-12.el8_2.4 | 0:7.61.1-12.el8_2.4 |
| Red Hat:rhel_eus:8.2::baseos | curl-debuginfo | before 0:7.61.1-12.el8_2.4 | 0:7.61.1-12.el8_2.4 |
| Red Hat:rhel_eus:8.2::baseos | curl-debugsource | before 0:7.61.1-12.el8_2.4 | 0:7.61.1-12.el8_2.4 |
+12
Same product
haxx: all recordsOther highest-scoring records for the same primary product.
- CVE-2021-22901curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session t51Plan
- CVE-2023-38039When curl retrieves an HTTP response, it stores the incoming headers so that
they can be accessed later via the libcurl headers API.47Plan
- CVE-2024-2398HTTP/2 push headers memory-leak45Plan
Published before and after this one in the same product
- ← EarlierCVE-2021-22926Aug 5, 2021 · libcurl-using applications can ask for a specific client certificate to be used in a transfer.35Monitor
- ← EarlierCVE-2021-22946Sep 29, 2021 · A user can tell curl >= 7.20.0 and <= 7.78.0 to require a successful upgrade to TLS when speaking to an IMAP, POP3 or FTP server (`--ssl-req31Monitor
- Later →CVE-2022-22576May 26, 2022 · An improper authentication vulnerability exists in curl 7.33.0 to and including 7.82.0 which might allow reuse OAUTH2-authenticated connecti33Monitor
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 |
|---|---|---|
| alpine:curl | 7.79.0-r0 · Alpine:v3.11 | Package registry (OSV) |
| debian:curl | 7.79.1-1 · Debian:12 | Package registry (OSV) |
| opensuse:curl | 7.66.0-lp152.3.24.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:curl-mini | 7.66.0-lp152.3.24.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| red hat:curl | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:curl-debuginfo | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:curl-debugsource | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:curl-minimal-debuginfo | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:libcurl | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:libcurl-debuginfo | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:libcurl-devel | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:libcurl-minimal | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:libcurl-minimal-debuginfo | 0:7.61.1-18.el8_4.2 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:rh-dotnet31-curl | 0:7.61.1-22.el7_9 · Red Hat:rhel_dotnet:3.1::el7 | Package registry (OSV) |
| red hat:rh-dotnet31-curl-debuginfo | 0:7.61.1-22.el7_9 · Red Hat:rhel_dotnet:3.1::el7 | Package registry (OSV) |
| red hat:rh-dotnet31-libcurl | 0:7.61.1-22.el7_9 · Red Hat:rhel_dotnet:3.1::el7 | Package registry (OSV) |
| rocky linux:curl | 0:7.61.1-18.el8_4.2 · Rocky Linux:8 | Package registry (OSV) |
| suse:curl | 7.60.0-25.1 · SUSE:Linux Enterprise High Performance Computing 15-ESPOS | Package registry (OSV) |
| suse:curl-openssl1 | 7.37.0-70.74.1 · SUSE:Linux Enterprise Server 11-SECURITY | 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).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-22-0552 · Aug 15, 2022(RedHat Güvenlik Güncellemesi)
- TR-22-0436 · Jun 20, 2022(IBM Güvenlik Bildirimi)
- TR-22-0215 · Mar 11, 2022(Siemens Güvenlik Bildirimi)
- TR-22-0167 · Feb 23, 2022(RedHat Güvenlik Güncellemesi)
- TR-22-0122 · Feb 9, 2022(Microsoft Güvenlik Güncellemesi)
- TR-22-0030 · Jan 12, 2022(Microsoft Güvenlik Güncellemesi)
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.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- none
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-310 · Cryptographic IssuesCVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/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.
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 (15 more)Show less
- cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
- lists.debian.org/debian-lts-announce/2021/09/msg00022.html
- lists.debian.org/debian-lts-announce/2022/08/msg00017.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOAK4X73EJTAPTSVT7IRVDMUWVXNWGD/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLEC6YVEM2HWUBX67SDGPSY4CQB72OE/
- security.gentoo.org/glsa/202212-01
- security.netapp.com/advisory/ntap-20211029-0003/
- support.apple.com/kb/HT213183
- www.debian.org/security/2022/dsa-5197
- www.oracle.com/security-alerts/cpuapr2022.html
- www.oracle.com/security-alerts/cpujan2022.html
- www.oracle.com/security-alerts/cpujul2022.html
- www.oracle.com/security-alerts/cpuoct2021.html
- cert-portal.siemens.com/productcert/html/ssa-389290.html
- cert-portal.siemens.com/productcert/html/ssa-398330.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.