VulnerabilityPublished 22 Jul 2026

CVE-2026-59920: STOMP CONNECT Frame Header Injection in Netty

Affects io.netty:netty-codec-stompSource GCVE Database

Not known to be exploited · CVSS 6.5 Medium : upgrade to 4.2.16.Final when convenient.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 35% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.2.16.Final, 4.1.136.Final

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade io.netty:netty-codec-stomp to 4.2.16.Final; io.netty:netty-codec-stomp to 4.1.136.Final.

Affected software

Product	Affected	Fixed in
Mavenio.netty:netty-codec-stomp	Affected >=4.2.0.Final <4.2.16.Final	Fixed in 4.2.16.Final
Mavenio.netty:netty-codec-stomp	Affected <4.1.136.Final	Fixed in 4.1.136.Final

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

# Security Vulnerability Report: STOMP CONNECT Frame Header Injection in Netty ## 1. Vulnerability Summary | Field | Value | |-------|-------| | **Product** | Netty | | **Version** | 4.2.12.Final (and all prior versions with codec-stomp) | | **Component** | `io.netty.handler.codec.stomp.StompSubframeEncoder` | | **Vulnerability Type** | CWE-93: Improper Neutralization of CRLF Sequences / CWE-113: Improper Neutralization of CRLF in HTTP Headers | | **Impact** | STOMP Header Injection / Authentication Bypass | | **CVSS 3.1 Score** | **6.5 (Medium)** | | **CVSS 3.1 Vector** | `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N` | | **Attack Vector** | Network | | **Attack Complexity** | Low | | **Privileges Required** | Low | | **User Interaction** | None | | **Scope** | Unchanged | | **Confidentiality Impact** | None | | **Integrity Impact** | High | | **Availability Impact** | None | ## 2. Affected Components - `io.netty.handler.codec.stomp.StompSubframeEncoder` — `encodeHeaders()` method (lines 174-200) - `io.netty.handler.codec.stomp.StompSubframeEncoder` — `shouldEscape()` method (lines 214-216) ## 3. Vulnerability Description The Netty STOMP codec encoder (`StompSubframeEncoder`) intentionally skips the `escape()` function for `CONNECT` and `CONNECTED` commands. This means that newline characters (`\n`) in header values of CONNECT frames are written directly to the output, allowing an attacker to inject additional STOMP headers. ### Root Cause In `StompSubframeEncoder.java`, the `shouldEscape()` method (lines 214-216) explicitly excludes CONNECT and CONNECTED commands from escaping: ```java private static boolean shouldEscape(StompCommand command) { return command != StompCommand.CONNECT && command != StompCommand.CONNECTED; } ``` When `shouldEscape()` returns `false`, header values are written without any escaping (line 195): ```java CharSequence headerValue = shouldEscape ? escape(entry.getValue()) : entry.getValue(); ByteBufUtil.writeUtf8(buf, headerValue); // Raw \n written to output buf.writeByte(StompConstants.LF); ``` For other commands (SEND, SUBSCRIBE, etc.), the `escape()` method (lines 218-240) correctly converts `\n` to `\\n`, `\r` to `\\r`, `:` to `\\c`, and `\\` to `\\\\`. ### STOMP Specification Context and Security Analysis The STOMP 1.2 specification (Section 10, Value Encoding) states that CONNECT and CONNECTED frames should **not use escaping**, to maintain backwards compatibility with STOMP 1.0 clients that do not understand escape sequences. **However, "no escaping" does not mean "no validation".** The specification's intent is that CONNECT headers should not use the `\n` → `\\n` escape notation. It does **not** mandate that implementations must accept raw newline characters within header values. There is a critical distinction: - **Escaping** = converting `\n` to `\\n` in the wire format (spec says: don't do this for CONNECT) - **Validation** = rejecting header values that contain `\n` (spec does not prohibit this) Netty's implementation conflates these two concepts: by skipping `escape()`, it also skips **all** protection against newline injection. The correct behavior would be to skip escaping but still **reject** values containing raw newline characters, since such values are inherently malformed — no legitimate STOMP 1.0 or 1.2 header value should contain a raw `\n`. This is analogous to Netty's own SMTP fix (GHSA-jq43-27x9-3v86): SMTP parameters don't need escaping either, but Netty added validation to reject CRLF in parameters. The same principle should apply here. **Additionally**, Netty's own test suite explicitly validates this non-escaping behavior in `StompSubframeEncoderTest.java:126-143` (`testNotEscapeStompHeadersForConnectCommand`), confirming that this is a deliberate design choice — but the test only verifies that escaping is skipped, not that injection is possible. The security implications were not considered. **Summary**: The vulnerability exists because: 1. Header values in CONNECT frames are **neither escaped nor validated** for newlines 2. A raw newline in a header value creates a **new header line** on the wire 3. The STOMP broker parses each line as a separate header 4. The fix should **validate** (reject `\n`) rather than **escape** (convert `\n` to `\\n`), maintaining spec compliance ## 4. Exploitability Prerequisites This vulnerability is exploitable when **all** of the following conditions are met: 1. The application uses Netty's `codec-stomp` module to encode STOMP frames 2. User-controlled input is placed into header values of a `CONNECT` or `CONNECTED` frame 3. The application does **not** perform its own newline sanitization 4. The downstream STOMP broker processes the injected headers (broker-dependent) **Typical affected use cases**: - STOMP proxy/gateway applications that forward or construct CONNECT frames with user-supplied credentials - Web-to-STOMP bridge applications (e.g., WebSocket-STOMP proxies) where login/passcode

CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection') (opens in a new tab)
Base weaknessOWASP Top 10 A05:2025: Injection (opens in a new tab)
The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
Implementation
Avoid using CRLF as a special sequence.
Implementation
Appropriately filter or quote CRLF sequences in user-controlled input.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
Attack patterns
Command Delimiters (opens in a new tab)
Web Server Logs Tampering (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-93

Technical details

References

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